UNIVERSITY  OF  CALIFORNIA 
AT  LOS  ANGELES 


THE 

SOURCES    AND   MODES 

OF 

INFECTION 


By 


CHARLES    V.    CHAPIN,    M.D.,    Sc.  D. 

SUPERINTENDENT   OF   HEALTH,    PROVIDENCE,    R.  I. 
AUTHOB    OF   "municipal  SANITATION   IN   THE   UNITED   STATES" 


7-^/61 


SECOND  EDITION  REVISED   AND  ENLARGED 
FIRST    THOUSAND 


NEW  YORK 

JOHN  WILEY  &  SONS 
Londok:    chapman   &   HALL,  Limited 

1912 


^  9  «  S      4 


Copyright,  1910,  1912, 
By  CIIAELES  V.  CHAPIN 


SStanbopc  lprc«B 

r.    N.    CILSON     COUPAIfT 
BOSTON.     US.  A. 


\o^'/o 


PREFACE. 


This  volume  is  intended  to  indicate  the  principles  which 
should  guide  sanitary  practice,  and  to  show  how  recent  labo- 
ratory work  and  the  epidemiological  study  of  disease  have 
modified  these  principles.  When  I  began  work  as  health  offi- 
cer in  1884  the  filth  theory  was  still  in  favor,  and  it  was 
generally  believed  that  the  germs  of  disease  commonly  grew 
in  decaying  organic  matter.  Yet  contagion  was  recognized 
as  an  important  factor  in  the  spread  of  disease,  and  the  isola- 
tion of  the  sick  was  more  and  more  insisted  upon.  Fifteen 
years  ago  probably  most  health  officials  believed  that  the 
contagious  diseases  could  be  completely  stamped  out  if  only 
all  persons  sick  with  them  could  be  isolated.  The  air  was 
thought  to  be  the  chief  medium  for  their  transmission,  and 
fomites  the  mechanism  for  their  passage  from  place  to  place. 
Sanitary  practice  was  based  on  these  premises. 

My  own  views  concerning  these  matters  became  greatly 
modified  year  by  year,  partly  owing  to  the  rapidly  accumu- 
lating knowledge  of  bacteria  and  other  disease-producing 
organisms,  and  partly  owing  to  direct  observations  on  the 
manner  in  which  the  infectious  diseases  are  disseminated,  and 
on  the  effect  of  preventive  measures. 

It  now  appears  that  the  growth  of  disease  germs  outside  of! 
the  body  is  not  frequent  enough  to  be  an  important  factor  inj 
the  causation  of  disease,  but  their  growth  in  the  body  with- 
out causing  sickness,  their  latency  as  it  were,  often  for  many 
months,  is  a  factor  of  very  great  significance.  We  know  now 
that  direct  contact  with  the  sick,  or  with  healthy  carriers  of 
disease  germs,  is  an  exceedingly  frequent  mode  of  transmis- 
sion, and  that  infection  by  means  of  the  air,  or  from  infected 
articles,  is  not  nearly  as  common  as  was  formerly  believed. 


IV  PREFACE 

We  are  now  better  able  than  ever  before  to  attribute  to  water 
and  milk  their  proper  share  in  the  distribution  of  infection. 
The  recent  discovery  of  the  transmission  of  disease  by  insects 
gives  us  entirely  new  and  most  effective  means  of  combating 
disease.  It  is  time  that  sanitary  measures  directed  against 
the  infectious  diseases  should  be  modified  to  correspond  with 
existing  knowledge.  Present-day  theories  and  present-day 
practice  are  maintained  largely  by  tradition,  and  to  facilitate 
the  adaptation  of  practice  to  the  facts  as  we  now  know  them, 
is  the  purpose  of  this  book.  Some  modifications  of  sanitary 
practice  are  suggested,  but  no  attempt  is  made  to  discuss 
details;  rather  are  general  principles  presented,  which  it  is 
believed  ought  to  guide  administrators  in  their  work. 

While  some  of  the  following  pages  may  seem  rather  radical 
to  many,  I  believe  that  practically  all  laboratory  workers  will 
agree  with  the  contents  of  the  first  chapter,  and  that  a  large 
number  of  bacteriologists  and  health  officers  are  convinced  of 
the  great  importance  of  "  carriers  "  and  mild  unrecognized 
cases.  The  tendency  among  many,  too,  is  to  lay  less  emphasis 
on  infection  by  fomites,  though  perhaps  few  are  ready  to 
give  up  routine  terminal  disinfection  for  the  common  infec- 
tious diseases.  So  also  there  are  very  many  careful  observers 
who  are  attril^uting  more  and  more  importance  to  what  is 
generally  called  contact  infection. 

The  public  health  administrator  is  placed  at  great  disad- 
vantage ])ecause  he  is  obliged  to  base  his  acts  on  knowledge 
which  is  far  from  exact.  The  laboratory  workers  have  accu- 
mulated a  vast  mass  of  quite  exact  data  in  regard  to  the  caus- 
ative relation  of  bacteria  and  ]irotozoa  to  disease,  and  no  one 
appreciates  this  more  than  the  writer,  but  there  are  many 
problems  which  the  laboratory  men  cannot  solve,  and  many 
others  which  thoy  have  failed  to  solve.  The  epidemiologist 
must  study  in  the  field  the  way  in  which  disease  is  caused. 
He  must  use  the  statistical  method,  and  the  application  of 
statistical  tnetliods  to  epidemiology  is  more  difficult  and  less 
attractive  than  laboratory  experiment. 


PREFACE  V 

We  need  to  measure  more  carefully  the  relative  importance 
of  different  sources  of  disease  and  different  modes  of  infec- 
tion. It  is  not  so  important  to  know  that  typhoid  bacilli 
live  in  water  for  weeks,  as  it  is  to  know  that  99  per  cent  die 
in  one  week.  It  is  not  enough  to  discover  that  diphtheria 
bacilli  can  be  recovered  from  articles  in  the  sick-room;  we 
must  learn  how  often  they  are  found  and  how  often  disease 
is  traced  to  such  a  source.  We  have  for  years  been  much 
alarmed  because  tubercle  bacilli  are  found  in  milk,  but  since 
a  serious  effort  has  been  made  to  measure  the  actual  danger, 
the  alarm  has  greatly  diminished.  Doubtless  the  house  fly 
has  been  the  cause  of  typhoid  fever,  but  in  what  percentage 
of  cases  we  are  profoundly  ignorant.  Healthy  carriers  of 
diphtheria  have  certainly  transmitted  the  disease  to  others, 
and  we  should  earnestly  try  to  determine  the  amount  of 
diphtheria  caused  in  this  way.  The  attempt  is  made  in  the 
following  pages  to  estimate  roughly,  with  the  very  imperfect 
material  now  available,  the  relative  importance  of  different 
factors  in  the  extension  of  infectious  diseases.  The  conclu- 
sions must  to  a  large  extent  be  merely  tentative,  and  as 
indicating  lines  for  further  study. 

I  am  under  great  obligations  to  my  friends  Dr.  H.  W.  Hill 
and  particularly  Prof.  F.  P.  Gorham  for  many  suggestions 
and  criticisms,  but  neither  is  to  be  considered  at  all 
responsible  for  any  of  the  views  presented. 

The  book  is  intended  primarily  for  health  officers  and  phy- 
sicians, but  it  is  hoped  that  many  others  will  find  some  parts 
interesting  and  suggestive. 

CHARLES    V.  CHAPIN. 

Providence,  April,  1910. 


PREFACE  TO  SECOND  EDITION. 


So  much  new  material  has  accumulated  since  the  appear- 
ance of  the  first  edition  that  it  has  been  thought  best  to  re- 
write several  parts  of  the  book.  Thus,  recent  experiments 
and  particularly  the  observation  that  bacteria  fresh  from 
the  body  are  usually  less  resistant  than  are  "cultured" 
germs,  indicate  that  the  life  of  bacteria  outside  the  body  is 
even  shorter  than  was  supposed.  It  is  in  regard  to  carriers 
that  literature  has  been  accumulating  most  rapidly  and 
several  comprehensive  articles,  as  well  as  very  numerous 
reports  of  carrier  infection,  leave  no  room  for  doubt  that  in 
many  diseases,  as  diphtheria,  cholera,  typhoid  fever  and 
cerebro-spinal  meningitis,  the  carrier  is  a  very  important, 
if  not  the  most  important,  factor  in  the  spread  of  the  disease. 
Also  recent  work  has  shown  that  contact-  with  carriers  is 
quite  likely  to  be  the  key  to  the  epidemiology  of  poliomyelitis. 
New  evidence  has  been  presented  concerning  the  carriage 
of  infection  by  milk  and  also  by  water,  but  I  cannot  see  that 
the  reality  of  the  Mills-lleincke  phenomenon,  which  depends 
upon  the  influence  of  water  on  so  many  forms  of  disease, 
has  yet  been  established.  Much  work  during  the  past  two 
years  has  been  devoted  to  insects  as  carriers  of  infection  and 
several  additional  diseases  have  been  shown  probably  to  be 
so  transmitted.  One  of  the  most  interesting  of  these  is 
typhus  fever,  and,  if  recent  work  is  substantiated,  much 
light  will  be  thrown  on  its  epidemiology.  While  there  is 
more  evideiice  than  there  Avas  tiiat  the  fly  is  a  factor  in  the 
spread  of  tlui  fecal-borne  diseases,  there  docs  not  as  yet  seem 
to  be  much  warrant  for  the  rather  sensational  literature 
willi  which  the  public  is  deluged.  Studies  in  hospitals 
and  elsewhere  have  confirmed  the  belief  that  air  is  of  minor 


PREFACE   TO  SECOND  EDITION  VU 

importance  in  the  spread  of  disease.  The  views  presented 
in  the  first  edition  in  regard  to  the  inutility  of  isolation 
under  many  conditions,  and  in  regard  to  the  small  importance 
of  fomites,  were  somewhat  novel  and  it  was  suspected  that 
they  might  be  subjected  to  considerable  criticism,  but  such 
does  not  seem  to  have  appeared,  and  I  still  believe  that, 
while  isolation  and  bedside  disinfection  will  in  the  future 
continue  to  be,  when  scientifically  applied,  of  the  utmost 
importance,  much  of  the  routine  practice  of  health  officials 
needs  to  be  profoundly  modified. 

Charles  V.  Chapin. 
Providence,  July,  1912. 


CONTENTS. 


CHAPTER   I. 

LIFE    OF   DISEASE    GERMS    OUTSIDE    OF    THE    BODY. 

PAGE 

Review  of  evidence  of  growth  of  disease  germs  outside  of  the 
body,  anthrax,  black  leg,  tetanus.  —  Typhoid  baciUi  in  soil,  feces, 
water,  ice,  oysters,  milk.  — ■  Epidemiological  evidence  relating  to 
typhoid  fever.  —  Evidence  relating  to  cholera,  Mediterranean 
fever,  plague,  dysentery,  bacteria  of  suppuration,  dip^hthprja  and 
various  other  diseases.  —  Reasons  for  former  belief  in  "  filth  theorj- "  ^^ 
of  disease.  —  Epidemiological  evidence  against  soil  infection.  — 
Conclusions.  — ■  Relations  of  these  views  to  pubhc  sanitation 1 

CHAPTER   n. 

CARRIERS    AND    MISSED    CASES. 

Importance  of  the  subject.  —  Evidence  of  the  occm-rence  of  ^ — 
carriers  and  missed  cases,  and  reference  to  disease  caused  by 
them  in  typhoid  fever,  cholera,  dysentery,  cerebro-spinal  menin- 
_gi^is,  diphtheria,  glanders,  influenza,  pneumonia,  gonorrhea, 
tuberculosis,  leprosy,  suppuration,  tetanus,  scarlet  fever,  small- 
pox, measles,  protozoan  diseases  such  as  cattle  fever,  malaria, 
sleeping  sickness,  nagana,  ^yphilis,  amebic  dysentery,  pohomye- 
Utis  and  yellow  fever.  —  Review  of  evidence.  —  Conclusions. ...       33 

CHAPTER   III. 

LIMITATIONS    TO    THE    VALUE    OF    ISOLATION.   ^-^ 

The  number  of  carriers  and  missed  cases.  —  Not  reahzed  by 
health  officials.  —  Failure  of  isolation  in  Providence.  —  Hospital- 
ization has  not  materially  lessened  infectious  disease.  —  Less 
isolation  followed  by  less  diphtheria  in  Providence.  — -  Failure  of 
isolation  in  institutions.  —  Failm-es  in  the  isolation  of  measles,  of 
cerebro-spinal  meningitis,  of  smallpo.x.  —  Failure  due  to  carriers 
and  missed  cases.  —  Difficulties  in  the  isolation  of  diphtheria.  — • 
Absolute  isolation  not  possible.  —  Moderate  isolation  sufficient. 

—  Infection  not  so  easy  as  was  believed.  —  Isolation  effective  at  \/^ 
the  beginning  of  an  outbreak,  rarely  later.  —  The  more  carriers 
the  less  effective  is  isolation.  —  True  value  of  isolation  hospitals. 

—  Details  of  home  isolation.  —  Summary 133 


X  CONTENTS 

CHAPTER  IV. 

INFECTION   BY    CONTACT. 

PAGE 

Transmission  of  gonorrhea  by  indirect  contact.  —  Of  syphilis 
in  the  same  way.  —  Typhoid  fever  spread  by  contact.  —  Reasons  i^^^ 
why  contact  infection  has  been  disregarded.  —  Mode  of  contact 
infection  in  typhoid  fever.  —  Contact  infection  in  dysentery.  — 
Cholera.  —  Anchylostomiasis.  —  Gonorrhea.  —  Transfer  of  nasal 
and  oral  secretions  by  contact.  —  Presence  of  germs  in  secretions 
and  on  various  objects.  - —  Diseases  do  not  spread  from  family  to 
family  in  tenements.  —  No  cross  infection  in  hospitals  except  by 
contact.  —  Contact  infection  in  tuberculosis.  —  Protection  from 
contact  infection  a  personal  matter.  —  Need  for  urging  personal 
cleanliness 164 

CHAPTER   V. 

INFECTION   BY   FOMITES. 

Definition.  —  Fomites  and  yellow  fever.  —  Examples  of  alleged 
fomites  infection.  —  Infection  by  clothing,  rooms,  rags,  money.  — 
Fomites  infection  in  tetanus,  antlu*ax,  typhoid  fever,  diphtheria, 
plague.  —  No  evidence  that  fomites  are  of  much  im{)ortance.  — 
Reasons  for  belief  in  fomites.  —  Effect  of  drying  on  bacteria  of 
different  kinds.  —  The  finding  of  bacteria  on  fomites.  —  Drying 
of  vaccine  and  smalI{)ox  virus.  — •  Summary  of  bacteriological  (evi- 
dence. —  Experimental  work  with  y(!llow  fever,  plague.  —  Results 
of  abandoning  disinfection  after  scarlet  fever  and  diphtheria  in 
Providence.  —  Disinfection  in  other  diseases.  —  School  disinfec- 
tion. —  Views  of  other  writers.  —  Conclusions 212 

CHAPTER  VI. 

INFECTION    BY   AIR. 

Alleged  aerial  transmission  of  small[)ox,  s(!ai-let  fever,  diph- 
theria, ty|)hoid  fever,  influenza,  measles.  —  Hosi)ital  experiments 
in  aerial  transmission.  —  Transmission  of  typhus  fever  and  plague. 

—  History  of  surgical  teclmi<]ue  shows  that  air-borne  infection 
is  of  little  moment.  —  Air-l)orn(^  anthrax.  —  Bacteria  not  given 
off  from  moist  surfaces.  —  liticteria  carried  in  dust.  —  Dust  and 
the  germs  of  typhoid  fever,  diphtheria,  plague.  —  Dust  and 
tubercle  bacilli.  —  Finding  of  tubercle  ba(;illi  in  dust.  —  Other 
bacteria  in  (hist .  —  Drojjlet  inf(U!t  ion.  —  Finding  of  bacteria  in  air. 

—  Expcriinciilal   work   with    tul)ercul()sis,    Mediterranean   fever, 

ant  lirax,  plague.  —  ( 'oiichisiotis 259 


CONTENTS  XI 

CHAPTER  VII. 

INFECTION   BY   FOOD    AND   DRINK. 

PAGE 

The  Broad  Street  weU.  —  North  Boston  well.  —  Typhoid  fever 
due  to  water.  —  Cholera,  dysentery,  diarrhea.  — ■  The  Mills- 
Reincke  phenomenon.  —  Malaria  and  yellow  fever.  —  Purification 
of  water.  —  Ice.  —  Milk,  number  of  outbreaks.  —  Mode  of  infec- 
tion of  the  milk.  —  Typhoid  fever,  scarlet  fever,  diphtheria.  — 
Ice  cream.  —  Butter.  —  Streptococcus  sore  throat  and  milk.  — 
Tuberculosis  and  milk,  evidence  of  infection.  —  Bacilh  in  market 
milk.  —  Amount  of  tuberculosis  due  to  milk.  —  Mediterranean 
fever,  anthrax,  foot-and-mouth  disease,  rabies.  —  Diarrhea.  — 
Infection  by  meat.  —  Infection  by  shellfish.  —  Crawfish.  — 
Watercress.  —  Celery 316 

CHAPTER   VIII. 

INFECTION   BY   INSECTS. 

Insects  as  biological  and  as  mechanical  carriers.  —  Pioneer 
work  of  Smith  and  Kilborne  in  cattle  fever.  —  Malaria.  —  Modes 
of  control:  quinia,  isolation,  screening;  mosquito  reduction; 
practical  results.  —  Yellow  fever  carried  by  mosquitoes,  not  by 
fomites.  —  Control  of  yeUow  fever;  quarantine,  isolation;  mos- 
quito control;  practical  results.  —  Filariasis,  sleeping  sickness, 
kala-azar,  dengue,  pellagra,  opilacoa,  pappataci  fever,  oriental 
sore,  typhus  fever,  relapsing  fever,  Rocky  Mountain  fever.  — 
Bubonic  plague  and  fleas.  —  Anthrax.  —  Carriage  of  bacteria  on 
the  bodies  of  insects.  —  Cockroaches  and  other  insects.  —  FUes, 
experimental  work.  —  Bacteria  found  on  flies.  —  Habits  and 
species.  —  Transmission  of  disease,  murrina,  tuberculosis,  cholera, 
dysentery,  diarrhea.  —  Fhes  and  typhoid  fever,  local  and  seasonal 
distribution.  —  Evidence  against  theory.  —  Epidemiological  evi- 
dence in  favor  of  causal  relation.  —  Privies,  flies  and  typhoid 
fever.  —  Conclusions 380 


THE   SOURCES   AND   MODES  OF 
INFECTION. 


CHAFPER  1. 

LIFE  OF    DISEASE   GERMS   OUTSIDE   OF    THE    BODY 

Former  Theories.  —  From  time  immemorial  miasms,  ma- 
larias, vapors  and  emanations,  gaseous  or  otherwise,  have 
been  believed  to  be  the  frequent  cause  of  disease.  These 
miasms  were  thought  to  arise  from  stagnant  marshes,  decay- 
ing vegetation,  putrid  animal  matter,  and  indeed  filth 
of  every  kind.  This  belief  in  the  extra-corporal  origin  of 
disease  reached  its  widest  acceptance  about  the  middle  of 
the  nineteenth  century.  The  rise  of  the  germ  theory  greatly 
strengthened  it.  The  discovery  of  bacteria  and  of  their 
wide  distribution  and  almost  universal  growth  in  dead 
organic  substances,  and  the  theory  that  these  bacteria  were 
the  real  cause  of  disease,  led  men  to  look  for  the  source  of 
disease  outside  of  the  body,  and  chiefly  in  dead  animal  and 
vegetable  matter.  With  the  passing  of  the  germ  theory  as 
a  theory,  and  with  the  demonstration  of  the  parasitic  nature 
of  so  many  of  our  most  important  and  dreaded  diseases,  the 
opportunity  was  afforded  for  studying  in  detail  the  bacteria 
and  protozoa  which  are  the  specific  causes  of  these  diseases. 
Much  has  been  done  by  laboratory  workers  to  unravel  the 
life  history  of  these  minute  forms,  and  it  is  well  for  us  to 
examine  the  knowledge  thus  gained,  and  also  the  newer 
epidemiological  observations  on  the  spread  of  the  infectious 
diseases,  and  in  the  light  of  these  data  question  the  belief 
that  these  diseases  have  their  origin  in  the  outer  world  rather 

1 


2  THE  SOURCES  AND  MODES  OF  INFECTION 

than  in  the  bodies  of  men  or  animals.    Let  us  consider  some 
of  these  diseases  in  detail. 

Anthrax  is  not  common  in  the  United  States,  but  it  is  of 
much  interest  from  a  scientific  standpoint.  It  was  the  first 
disease  definitely  proved  to  be  caused  by  bacteria.  It  is 
of  particular  interest  in  this  connection  because  a  relation 
to  the  soil  has  been  better  established  for  this  than  for  any 
other  disease.  Practically  all  writers  are  agreed  that  the 
soil  may  become  infected  with  anthrax,  and  remain  so  for 
a  long  time,  and  that  animals  pastured  upon  such  soil  con- 
tract the  disease  by  taking  the  bacteria  in  with  the  food, 
or  inspired  air,  or  through  abrasions  of  the  skin.  That  this 
soil  infection  is  not  the  sole,  or  perhaps  even  the  most  com- 
mon source  of  infection,  and  that  danger  from  this  source 
has  perhaps  been  somewhat  exaggerated,  is  probably  true. 
Thus  Delepine  ^  from  studying  recent  outbreaks  in  Great 
Britain  is  convinced  that  the  disease  is  perpetuated  by 
a  more  or  less  direct  contact,  chiefly  with  unrecognized  or 
con(!ealed  cases,  and  that  there  is  no  necessity  for  supposing 
a  long  continued  soil  infection,  and  no  direct  evidence  for 
it  as  the  principal  source  of  the  disease.  McFadyean  ^  can- 
not trace  anthrax  in  Britain  to  the  soil,  and  thinks  it  im- 
probable that  it  grows  there,  or  it  would  be  more  common. 
Moreover  it  does  not  grow  well  under  60°.  Lcgge '  notes  that 
animal  anthrax  does  not  increase  in  the  summer  as  it  would 
be  likely  to  if  it  were  due  to  growth  in  the  soil.  Moore  *  does 
not  think  the  bacillus  maintains  a  saprophytic  existence. 
In  Louisiana''  the  extensive  outbreak  in  the  latter  years  of 
the  nineteenth  century  was  believed  to  be  due  to  some  extent 
to  food  infection,  and  to  a  large  extent  to  direct  inoculation 

'   Dch'pinf,  I'ul).  Iloultli,  1904-.''),  XVII,  491. 

^  M(l'"!i(lycan,  J.  Conip.  Putli.  iind  Therup.,  Edinh.  and  Lond.,  1903, 

XVI,  :ir,. 

»  LcKKo,  Liuicot,  Loud.,  1905,  I,  09.'). 
*  ]{cp.  Coinm.  of  Agric.  N.  Y.,  1907. 
'  Louisiimu  AKrifiiltural  Experiment  Sta.,  Bull.  No.  GO,  2d.  s.,  1900. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY        3 

by  a  species  of  horsefly,  Tabanus  lineola.  Outbreaks  of 
anthrax  have  occurred  every  few  years  in  Louisiana  for  over 
half  a  century,  and  persistent  soil  infection  has  been  alleged 
as  their  source.  Very  likely  it  is  so  to  a  certain  extent,  but 
on  the  other  hand  there  is  no  doubt  that  the  interval  be- 
tween the  outbreaks  may  well  be  bridged  over  by  a  more  or 
less  direct  connection  between  sporadic  and  unrecognized 
cases  occurring  in  the  interval.  That  such  cases  really  occur 
is  shown  by  Delepine's  investigations  of  similar  conditions 
in  England.  Nevertheless  almost  all  veterinary  and  medical 
writers  are  agreed  as  to  the  long  continued  soil  infection  of 
certain  areas.  Evidence  of  this  is  forthcoming  from  France, 
Germany,  England  ^  and  the  United  States.  In  England  such 
infective  areas  are  said  to  be  the  most  numerous  where  refuse 
from  mills  using  foreign  wools  is  used  for  manure.  In  this 
country  anthrax  is  believed  to  have  been  traced  to  morocco 
factories  on  the  Delaware  River  using  large  numbers  of 
foreign  skins. ^  Some  of  the  infected  Delaware  farms  had  new 
tenants  with  new  cattle  each  year,  but  infection  recurred. 
All  the  evidence  pointed  to  persistent  infection  of  the  soil. 
Similarly  infected  farms  or  fields  are  reported  from  New  Jer- 
sey,^ from  the  Genesee  valley  *  and  from  Louisiana.^  Law 
reports  that  200  cases  in  cattle,  and  3  in  human  beings  re- 
sulted in  the  space  of  two  weeks,  from  the  soil  infection  of  a 
limited  area.  Dr.  Leonard  Pearson  wrote  me  that  the  evi- 
dence is  conclusive  that  soil  infection  with  anthrax  has  existed 
in  a  number  of  places  in  Pennsylvania.  Two  instances  have 
recently  been  reported  which  seem  to  show  pretty  conclu- 
sively that  anthrax  bacilli  do  grow  in  small  ponds  under 

^  Poore,  The  Earth  in  Relation  to  the  Preservation  and  Destruction 
of  Contagia,  Lond.,  1902,  9-21. 

*  Delaware  Agricultural  Experiment  Sta.,  Bull.  No.  32,  1896,  6. 

'  Rep.  St.  Bd.  Health,  N.  J.,  1904,  5. 

<  Law,  Text-Book  of  Veterinary  Medicine,  Ithaca,  1902,  IV,  195. 

^  Louisiana  Agricultural  Experiment  Sta.,  Bull.  No.  60,  2d  8.,J!nsert^ 
opp.  345,  and  357. 


4  THE  SOURCES  AND  MODES  OF  INFECTION 

natural  conditions.  Dr.  J.  Sinclair  Holden,  health  officer  of 
Sudbury,  Co.  Suffolk,  England,  writes  that  in  1905  the  waste 
water  from  a  horsehair  factory  was  discharged  into  a  small 
pond.  There  was  evidently  some  seepage  from  this  pond  to 
another  about  20  feet  distant.  The  second  pond,  in  the  fol- 
lowing year,  was  found  to  be  so  abundantly  filled  with  the 
bacilli  of  anthrax  that  it  seemed  that  there  must  have  been 
free  reproduction.  Hastings  ^  also  reports  that  he  examined 
a  pond  which  had  received  anthrax-infected  tannery  refuse, 
and  that  this  was  teeming  with  the  vegetative  forms  of  the 
bacillus. 

While  there  is  a  good  deal  of  evidence,  apparently  conclu- 
sive, that  soil  may  remain  infected  with  anthrax  for  years, 
there  also  is  evidence  that  the  infection  after  a  time  disap- 
pears. Pasteur  records  instances  of  the  infection  dying  out 
after  a  lapse  of  some  years,^  and  in  Delaware  infection  did 
not  persist  on  all  the  infected  farms. ^  The  fact  that  anthrax 
has  appeared  at  so  many  isolated  points  in  England  and  the 
United  States,  and  though  in  the  majority  of  cases  soil  inocu- 
lation must  have  taken  place,  nevertheless  the  fact  that  the 
disease  has  never  become  widespread  or  long  persistent  locally 
is  sufficient  reason  for  the  conclusion  that  its  virus  does  not, 
in  these  countries  at  least,  find  a  suitable  soil.  If  it  increases 
at  all  in  the  soil  it  is  only  for  a  time,  and  the  tendency  is  for 
it  to  die  out.  In  other  words,  the  history  of  this  disease  is 
best  explained  on  the  hypothesis  that  the  soil  is  infected 
chiefly  if  not  exclusively  by  the  spores,  which  may  retain 
their  virulence  for  years,  but  which  rarely  germinate  in  the 
eartli. 

Charbon  Symptomatique.  —  Another  animal  disease  known 
as   black-leg,   or   in    Europe   as   charhon   symptomatique,   is 

'  HastinRH,  Paper  read  iit  mooting  of  Society  of  American  Bacteri- 
oloKiHtH,  1<M)S. 

'  I'oorc,  Tlu;  Karlli  in  Relation  (o  the  1 'reservation  and  Destruction 
of  Contagia,  Lond.,  lUO'i,  VA. 

'  Delaware  Agricultural  Experiment  Sta.,  Bull.  No.  32,  1896,  7. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY        5 

quite  prevalent  among  cattle  in  this  country.  Like  anthrax 
it  is  caused  by  a  bacillus  that  forms  spores.  Veterinarians 
are  agreed  that  soil  areas  become  infected  with  black-leg  and 
may  remain  so  for  some  time.  Undoubtedly  this  infection 
may  be  explained,  as  is  the  infection  by  anthrax,  as  due  simply 
to  the  resistance  of  the  spores,  and  does  not  necessarily  re- 
quire the  actual  multiplication  of  the  germs  in  the  soil. 

Tetanus  or  lockjaw,  even  before  it  was  known  to  be  due 
to  a  bacillus,  was  believed  to  occur  with  exceptional  fre- 
quency in  limited  areas.  It  has  been  stated  by  numerous 
writers  that  there  is  a  strip  of  land  near  Red  Bank,  New 
Jersey,  where  tetanus  is  decidedly  endemic.  The  disease  was 
also  said  to  be  formerly  extremely  common,  especially 
among  animals,  on  the  eastern  end  of  Long  Island,  but  that 
it  has  now  become  quite  rare  in  that  locality.  This  alleged 
local  prevalence  on  Long  Island  has  been,  in  this  country  at 
least,  one  of  the  most  frequently  used  arguments  in  sup- 
port of  soil  infection,  but  Overton'  has  shown  that  the 
published  statements  cannot  be  verified,  and  that  the  disease 
has  not  been  especially  prevalent  in  that  locality.  I  have 
corresponded  with  various  officials  in  New  Jersey,  but  have 
never  been  able  to  obtain  any  evidence  of  the  alleged  local 
infection  at  Red  Bank.  Tetanus  is  more  common  in  the 
southern  than  in  the  northern  parts  of  the  United  States, 
and  is  a  very  important  cause  of  death  in  the  West  Indies. 
Before  the  organization  of  the  present  efficient  health  depart- 
ment in  Havana  there  were  often  200  deaths  or  more  annually 
from  infantile  tetanus,  due  to  infection  of  the  navel.  It  has 
long  been  recognized  that  tetanus  follows  wounds  in  which 
dirt  is  forced  deep  into  the  tissues,  and  that  garden  earth  is 
especially  dangerous.  Even  well-established  evidence  of  per- 
sistent local  infection  does  not  prove  growth  in  the  soil.  It 
might  be  due  to  a  great  variety  of  causes. 

Thus  it  has  been  explained  that  the  bacilli  of  tetanus  are 
very  widely  distributed  because  these  bacteria  are  natural 
»  Overton,  Long  Island  M.  J.,  Brooklyn,  1907,  I,  176. 


6  THE  SOURCES  AND  MODES  OF  INFECTION 

inhabitants  of  the  healthy  intestines  of  domestic  animals, 
particularly  the  horse.  Hence  they  are  found  in  profusion 
wherever  the  manure  from  these  animals  falls,  and  soiled  skin 
and  clothing  are  not  likely  to  carry  them.  Theobold  Smith/ 
however,  says  that  there  is  no  evidence  that  the  tetanus 
bacilli  are  normal  inhabitants  of  and  multiply  in  the  intes- 
tines of  animals.  He  inclines  to  the  view  that  their  home  is 
in  the  soil.  Vincent^  after  introducing  tetanus  spores  into 
the  stomach  of  a  rabbit  could  find  no  evidence  of  multipli- 
cation, and  he,  too,  thinks  a  saprophytic  existence  probable. 
The  tetanus  bacillus  forms  spores  which  may  retain  their 
vitality  for  16  years,  so  that  it  is  not  surprising  that  lands 
have  been  known  to  remain  infected  for  several  years. ^  These 
spores,  or  the  bacilli,  are  said  to  have  been  found  in  gelatine,* 
in  blank  cartridges,^  and  on  balls  of  lamp  wick  used  in  Havana 
for  tying  the  umbilical  cord."  *  While  the  soil,  and  dirt  gener- 
ally, contain  tetanus  bacilli  or  their  spores,  there  is  no  direct 
evidence  to  show  that  they  are  propagated  outside  of  the  body. 
The  fact  that  they  do  not  grow  in  the  presence  of  air  would 
indicate  that  this  is  not  the  case,  and  the  distribution  of  the 
disease  and  its  comparative  rarity  would  also  lead  to  this 
conclusion.  It  is  not,  of  course,  to  be  denied  that  the  tetanus 
bacillus  may  lead  a  saprophytic  existence.  It  is  very  pos- 
sible that  it  may  do  so,  but  it  certainly  can  be  affirmed  that 
at  present  we  have  no  proof  that  it  does  so,  and  all  observed 
facts  relating  to  the  bacillus,  or  the  disease  caused  by  it,  may 
be  explained  without  assuming  any  such  hypothesis. 

It  is  suggestive  that  the  pathogenic  bacteria  which  are 
oftenest  assumed  to  grow  in  the  soil  are  the  very  ones  the 

'  Theobold  Smith,  J.  Am.  Ass.,  Chicago,  1908,  L,  929. 
'  Vincent,  Compt.  rond.  Soc.  dc  ImoI.  Par.,  1908,  LXV,  12. 
»  Villar,  J.  Coiiip.  Path,  and  Thorap.,  ]':dinh.  and  Lend.,  1897,  XX. 
«  Tuck,  J.  Patli.  and  Bactoriol.  ICdinh.  and  Lend.,  1904,  IX,  38. 
'  JJollcy,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  466. 
"  Junta  Superior  de  Sanidad  dc  la  Isla  de  Cuba,  Suplemento  y  Noto 
Adicional,  1902-3,  4. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY        7 

spores  of  which  may  retain  their  vitality  for  years.  Is  it  not 
more  likely  that  it  is  persistence  of  spores,  rather  than  growth 
of  the  bacilli  themselves,  that  in  most  instances  maintains 
the  soil  infection  ? 

T3rphoid  Bacilli  in  Soil.  —  It  has  been  amply  demonstrated 
that  water,  milk,  soil  and  various  other  materials  are,  when 
sterile,  suitable  media  for  the  growth  of  the  typhoid  bacillus. 
But  this  fact  is  of  little  practical  importance,  as  sterile  mate- 
rials are  not  ordinarily  found  in  nature,  but  on  the  contrary 
almost  everything  which  could  possibly  be  considered  a  cul- 
ture medium  for  typhoid  and  other  disease  germs  is  swarming 
with  bacteria,  mostly  of  entirely  harmless  varieties.  There 
has  been  much  painstaking  work  to  determine  whether  ty- 
phoid bacilli  actually  do  grow,  or  even  retain  their  vitality, 
in  or  on  a  great  variety  of  substances.  The  difficulties  in 
this  sort  of  experimentation  are  considerable,  and  not  the 
least  is  that  of  picking  out  the  typhoid  bacillus  from  among 
other  forms.  Robertson^  and  Firth  and  Horrocks^  seem  to 
have  made  the  most  elaborate  experiments  in  regard  to  its 
growth  in  soil,  and  to  have  worked  under  more  natural  con- 
ditions than  most  observers.  Robertson  found  that  by 
moistening  soil  from  time  to  time  with  bouillon  he  could 
keep  the  bacillus  alive  for  11  months,  and  even  cause  it  to 
grow.  Firth  and  Horrocks  did  not  find  any  evidence  of 
increase  in  soil  under  a  great  variety  of  conditions.  When 
conditions  were  favorable  it  could  be  recovered  up  to  74  days. 
In  peat  it  could  only  be  recovered  after  13  days.  More 
recently  Mair^  has  been  able  to  recover  the  bacillus  from  un- 
sterilized  soil  in  large  numbers,  for  20  days,  and  in  small 
numbers,  up  to  70  or  80  days.  He  found  no  evidence  of 
increase.  Great  care  was  taken  not  to  introduce  any  nutri- 
tive medium  with  the  bacilli.  Unlike  most  observers,  Mair 
found  that  in  sterile  soil  the  bacilli  disappear  more  rapidly, 

1  Robertson,  Brit.  M.  J.,  Lond.,  1898,  I,  69. 

«  Firth  and  Horrocks,  Brit.  M.  J.,  Lond.,  1902,  II,  936. 

'  Mair,  J.  Hyg.,  Cambridge,  1908,  VIII,  37. 


8  THE  SOURCES  AND  MODES  OF  INFECTION 

in  1 1  days  in  fact.  He  believes  that  this  is  due  to  the  chem- 
ical composition  of  the  particular  soil  used.  Smith  ^  working 
with  similar  soil,  unsterilized,  could  not  recover  the  organism 
after  25  days,  and  the  average  duration  in  the  soil  was  15 
days.  Calvagno  and  Calderini  ^  spread  upon  the  soil  some 
typhoid  excreta.  It  was  found  that  the  bacilli  could  be 
recovered  from  the  surface  of  the  soil  for  12  to  20  days 
and  from  the  deeper  portions,  20  centimeters,  for  40  days. 
Most  observers,  as  Koch,^  Karlinski,'*  UfTelmann,^  Martin,^ 
Pfuhl  ^  and  others  agree  that  it  does  not  grow  in  soil, 
though  it  may  retain  its  vitality  at  times  for  months. 
Savage  ^  found  that  it  died  rapidly  in  tidal  mud,  though  a 
few  bacilli  could  be  recovered  after  five  weeks.  Klein  ^ 
could  not  find  the  organism  in  dead  animals  buried  in  earth, 
after  20  days,  but  Loesner  i"  found  it  after  96  days. 

Typhoid  Bacilli  on  Vegetables.  —  Recently  Creel  ^^  has 
investigated  the  chance  of  vegetables  becoming  infected 
with  typhoid  bacilli.  He  planted  radishes  and  lettuce  in 
soil  which  was  watered  two  or  three  days  later  with  a 
fecal  emulsion  mixed  with  a  24-hours-old  agar  culture  of 
the  typhoid  bacillus.  Some  of  the  plants  were  grown  in- 
doors and  some  in  the  open  air  more  or  less  exposed  to 
sunshine.     The  leaves  and  stems  were  examined  every  3 

'  Smith,  Rep.  on  Occurrence  of  Typhoid  Fever  in  Belfast,  1902, 
quoted  by  Mair. 

*  Calvagno  and  Calderini,  Ztschr.  f.  Hyg.  u.  Infectionskrankh., 
Leipz.,  1908,  LXI,  188. 

»  Koch,  Die  Bekampfung  dcs  Typhus,  Berl.,  1903,  14. 

*  Karlinski,  Arch.  f.  Ilyg.,  Miinchen  u.  Leipz.,  1891,  XIII,  302. 
»  Uffehnann,  C^entralbl.  f.  Bakteriol.  [etc.],  Jena,  1894,  XV,  133. 

«  Martin,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Loud.,  1900-1901,  XXX, 
508. 

">  Pfuhl,  Ztschr.  f.  Ilyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  555. 

'  Savage,  J.  Ilyg.,  Cambridge,  1905,  V,  14G. 

»  Klein,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1898-9,  XXVIII,  303. 

"  Loesner,  Arb.  a.  d.  k.  Gsndhtsamte,  Berl.,  189G,  XII,  448. 

»  U.  S.  Pub.  Health  and  Mar.  llosp.  Serv.,  Pub.  Health  Rep.,  1912, 
X.WII,  187. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY       9 

days  for  the  bacilli,  and  they  were  found,  but  not  constantly, 
for  periods  varying  from  10  to  31  days.  The  author  con- 
siders that  these  experiments  demonstrate  the  possibility 
Df  the  transmission  of  typhoid  fever  by  means  of  uncooked 
vegetables  grown  in  infected  soil,  and  so  they  do.  Yet  it 
often  happens  that  the  soil  is  manured  a  long  time  before 
the  seed  is  planted,  so  that  the  bacilli  have  a  chance  to  die 
out,  and  doubtless  often  the  conditions  are  less  favorable 
than  in  the  experiments,  owing  to  excessive  rains,  or  pro- 
longed drought,  or  very  hot  weather;  and  it  is  also  true 
that  the  use  of  fresh  night  soil  as  a  fertilizer  in  the  more 
civilized  countries  is  rapidly  diminishing,  so  that  it  is  not 
unlikely,  after  all,  that  raw  vegetables  are  only  occasionally 
a  source  of  typhoid  fever.  If,  too,  as  now  seems  probable, 
bacilli  in  feces  are  less  resistant  than  those  from  cultures, 
the  danger  would  be  less  than  at  first  sight  appears  from 
these  experiments.  There  can,  however,  be  no  doubt  that 
this  is  a  real  source  of  danger,  and  that  human  excrement 
should  not  be  used  for  fertilizing  vegetables  and  low-growing 
fruits  which  are  to  be  eaten  raw.  The  futility  of  attempting 
to  cleanse  them  by  ordinary  washing  or  rinsing  is  shown  by 
Creel,  who  without  success  tried  to  cleanse  a  lettuce  leaf  by 
three  washings  with  a  pipette  and  by  stirring  in  water. 

Typhoid  Bacilli  in  Feces. —  According  to  Park,i  typhoid 
bacilli  soon  die  out  in  feces,  usually  in  a  few  hours,  but  he 
has  recovered  them  up  to  the  tenth  day.  He  suggested  that 
this  variation  may  depend  on  the  constitution  of  the  feces. 
On  the  other  hand,  Levy  and  Kayser  ^  note  the  persistence 
of  typhoid  bacilli  in  a  cemented  privy  vault  up  to  5  months, 
and  Pfuhl  ^  recovered  them  after  3  months  from  feces  mixed 
with  garden  earth.     Delepine  ^  states  that  typhoid  bacilli 

1  Park,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  852. 
^  Levy  and  Kayser,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena, 
1902,  XXXIII,  489. 

*  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  555. 

*  Delepine,  Rep.  Health  of  Manchester,  1907,  82. 


10  THE  SOURCES  AND  MODES  OF  INFECTION 

will  survive  in  a  privy  for  a  year.  His  investigation  was 
made  in  1898,  13  months  after  the  use  of  the  privy  by  a 
patient.  Meanwhile  the  vault  had  been  disinfected  several 
times.  Apparently,  however,  its  use  by  a  carrier  was  not 
excluded.  Calvagno  and  Calderini  recovered  typhoid  ba- 
cilli from  a  privy  vault  for  30  days  and  from  a  barrel  for 
25  days.  Morgan  and  Harvey  ^  could  not  recover  typhoid 
bacilli  from  a  privy  vault  later  than  18  days.  Semple  and 
Greig^  found  that  urine  containing  60,000,000  bacilli  per 
cubic  centimeter  kept  at  80°  F.  was  free  from  them  in  72 
hours,  and  that  feces  under  similar  circumstances  lost  them 
in  96  hours.  Mosebach  ^  sought  for  typhoid  bacilli  in  privy 
vaults  belonging  to  houses  where  carriers  resided  but  where 
there  had  been  no  frank  case  of  typhoid  fever  for  years,  and 
had  no  difficulty  in  recovering  the  germs.  Johnstone  ^  in 
studying  the  Janet  Hill  outbreak,  which  was  probably  due 
to  carriers,  could  find  no  bacilli  in  6  samples  of  soil  from 
the  yard  of  a  house  where  there  had  been  persistent  typhoid 
fever.  Rogers  ^  found  that  the  bacillus  lived  only  a  few 
days  in  filtered  septic  tank  effluent. 

Typhoid  Bacilli  in  Water.  —  Jordan  and  Russell^  imitated 
natural  conditions  l^y  enclosing  inoculated  water  in  colloidal 
sacs  to  permit  of  osmosis,  and  these  were  placed  in  the 
Chicago  River,  a  sewage-polluted  stream.  They  could 
recover  the  bacilli  for  from  3  to  7  days  only.  Russell  and 
Fuller^  repeated  these  experiments  with  substantially  the 
same  results,  though  they  kept  the  bacillus  alive  in  lake 

'  Morgan  and  Harvey,  J.  Roy.  Army  Med.  Corps,  1909,  XII,  587. 

*  Semple  and  Greig,  So.  Memoirs,  Med.  and  San.  Dept.,  Gov.  India, 
1908,  XXXII,  40. 

»  Mosebach,  Centralbl.  f.  Bakferiol.  [etc.],  I  Abt.,  Jena,  1900,  LII, 
Orig.,  170,  77:3. 

*  .loliiislone,  R(>p.  Med.  Off.  Local  (Jov.  Bd.,  Lond.,  1909-10, 
XXXIX,  IGfi. 

'  l{og(Ts,  Brit.  M.  .1.,  Lond.,  VMi,  II,  0.39. 

«  .Ionian  and  RuhscII,  .1.  Infect,.  Dis.,  Ciiicago,  190t,  1,  641. 

»  RuBscll  and  Fuller,  J.  Infect.  Dis.,  Chicago,  1906  [Suppl.  No.  2],  40. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      11 

water  from  8  to  10  days.  Houston^  has  made  some  careful 
quantitative  studies  of  the  Ufe  of  the  typhoid  bacillus  in 
raw  London  tap  water.  In  eighteen  series  of  tests  the 
average  reduction  during  the  first  week  was  99.9  per  cent, 
but  a  few  could  be  recovered  up  to  the  eighth  week. 

More  recently  Houston-  has  compared  the  bacilli  fresh 
from  a  carrier  with  the  same  strain  after  cultivation  and  he 
found  that  while  the  former  usually  lived  over  5  weeks,  the 
latter  in  9  tests  died  in  1  week,  in  3  tests  in  2  weeks  and  in  1 
test  in  3  weeks.  He  also  drank,  without  bad  results,  on  10 
different  days  a  half  pint  of  water  to  each  half  pint  of  which 
had  been  added,  from  23  to  28  days  previously,  fresh  urine 
from  the  carrier  containing  218,000,000  bacilli. 

Morgan  and  Harvey^  came  to  a  similar  conclusion  as 
regards  the  comparative  viability  of  typhoid  bacilli  from 
cultures  and  from  excreta.  They  consider  that  cultures  are 
worthless  for  practical  tests  of  the  viability  of  the  bacillus. 
As  most  of  the  tests  have  been  made  with  cultures,  it  seems 
highly  probable  that  the  persistence  of  the  typhoid  bacillus 
outside  of  the  body  is  not  as  great  as  many  of  the  experi- 
ments would  indicate.  Houston  ^  has  made  careful  search 
for  typhoid  bacilli  in  raw  Thames  and  Lea  waters  which 
are  more  or  less  polluted  with  sewage.  From  215  samples 
of  water  aggregating  116,900  cubic  centimeters,  20,771 
colonies  were  isolated  for  study,  but  only  2  proved  to  be 
typhoid  bacilli.  These  examinations  continued  through 
the  year. 

Wilson  and  Dickson  *  report  that  they  have  developed  a 
new  method  for  isolating  the  typhoid  bacillus  from  water 
by  which  they  can  recover  a  single  bacillus  from  100  c.c.  of 
water.  They  claim  that  they  can,  by  their  method,  show 
the  presence  of  the  bacillus  when  other  methods  fail  to 

^  First  Rep.  on  Research  Work,  Met.  Water  Bd.,  Lond. 

2  Seventh  Rep.  on  Research  Work,  Met.  Water  Bd.,  Lond. 

3  Morgan  and  Harvey,  J.  Roy.  Army  Med.  Corps,  1909,  XII,  587. 
*  Wilson  and  Dickson,  J.  Roy  San.  Ins.,  Lond.,  1911,  XXXII,  9. 


12  THE  SOURCES  AND  MODES  OF  INFECTION 

reveal  it  and  that  conclusions  as  to  the  rapid  disappearance 
of  the  bacillus,  based  on  other  methods,  are  consequently 
erroneous.  They  found  that  the  typhoid  bacillus  could 
be  recovered  from  water  up  to  the  twenty-third  day. 
But  it  may  be  that  a  single  bacillus  in  100  c.c.  is  so 
extremely  unlikely  to  cause  infection  that  somewhat 
coarser  methods  may  yield  results  more  indicative  of  the 
practical  danger. 

Field  ^  found  that  typhoid  bacilli  would  survive  in  sea- 
water  for  from  6  to  8  days,  but  that  50  per  cent  died  in  24 
hours.  Herdman  and  Boyce  -  found  no  evidence  of  the  mul- 
tiplication of  the  typhoid  bacillus  in  sea-water  but,  on  the 
contrary,  it  entirely  disappeared  in  about  3  weeks,  the 
larger  part  of  the  reduction  taking  place  during  the  first 
few  days. 

Recent  careful  observations  have  shown  that  in  potable 
waters  typhoid  bacilli  are  able  to  survive  much  longer  in 
winter  than  in  summer.  Ruedigcr^  had  noticed  that  the 
number  of  colon  bacilli  in  the  river  supplying  Grand  Forks, 
N.  D.,  was  4  or  5  times  greater  in  winter  than  in  summer. 
Believing  that  the  excess  in  winter  was  due  to  the  longer 
life  of  the  bacilli  at  that  season  he  tested  the  question  by 
hanging  in  the  river  at  different  seasons  celloidin  sacs  con- 
taining large  numbers  of  typhoid  bacilli.  It  was  deter- 
mined that  in  the  winter,  when  the  river  was  covered  with 
about  30  inches  of  ice,  the  typhoid  bacilli  lived  5  or  6  times 
as  long  as  in  the  summer.  In  summer  he  floated  down  the 
river  two  dialyses  containing  large  numbers  of  bacilli  and 
after  54  hours  only  0.11  per  cent  was  left  in  one  and  0.013 
in  the  other.  Ruediger  attributes  the  greater  longevity 
in  winter  in  part  to  the  inter-relation  of  different  organisms 
:iim1  in  part  to  the  cutting  off  of  the  sun's  rays  by  the  ice. 
Houston''  placed  typhoid  bacilli  in  tanks  at  different  teraper- 

•  Ficlfl,  Rop.  Dopt.  Health,  City  of  Now  York,  1904,  I,  451. 

^  Ilcnliiiiin  and  Hoycic,  I{cp.  TlionipHon  Yates  Lab.,  1898-9,  I. 
'   lliie.iincr,  .1.  Am.  I'lih.  IlcalUi  Ass.,  1911,  I,  411. 

*  hJcveiitli  llcp.  on  Research  Work,  Med.  Water  Bd.,  Lond. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      13 

atures  and  found  that  a  reduction  which  took  place  in  2 
weeks  at  64.4°  F.  required  3  weeks  at  50°,  4  weeks  at  41° 
and  5  weeks  at  32°. 

-  Wheeler  finds  that  in  well  water  with  considerable  pollu- 
tion, at  room  temperature,  and  with  the  exclusion  of  light, 
a  considerable  increase  of  typhoid  organisms  may  take 
place.  Konradi  also  claims  that  this  bacillus  can  main- 
tain a  saprophytic  existence  in  water,  but  his  methods  have 
been  criticised,  and,  in  some  experiments  at  least  a  good 
deal  of  nutrient  material  was  added  to  the  water  with  the 
ocganisms.  The  report  on  typhoid  fever  in  the  District  of 
Columbia  ^  quotes  from  Kubler  and  Neufeld,  and  Stroezner 
and  Tavel,  instances  of  alleged  longevity  of  the  typhoid 
bacillus  in  well  water  or,  in  Tavel's  case,  in  tap  water,  but 
secondary  contact  infection  was  not  in  any  instance  abso- 
lutely excluded.  On  the  other  hand,  the  infection  in  a 
reservoir  in  Scranton  was  proved  to  have  died  out  within  8 
weeks. - 

PfuhP  found  bacilli  in  tap  water  after  28  days,  but  not 
after  31  days.  In  artificially  inoculated  seltzer  water  it 
lived  for  27  days.  Hill,^  however,  could  not  recover  it  from 
various  carbonated  "  soft  drinks  "  after  14  hours. 

Typhoid  Bacilli  in  Ice.  —  Various  writers  have  studied  the 
life  of  typhoid  bacilli  in  ice,  and  Prudden,^  Winslow,®  Park,^ 
Jordan,  Russell  and  Zeit,*  Clark,^  Smith  and  Swingle^''  and 
Wheeler^^  have  shown  that  they  tend  to  disappear  gradually, 

1  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Hyg.  Lab.  Bull.  No.  35,  178. 

2  N.  York  M.  J.  [etc.],  1907,  LXXXV,  1025. 

3  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  55. 
*  Hill,  Rep.  Bd.  of  Health,  Bost.,  1904,  53. 

5  Prudden,  Med.  Rec,  N.  Y.,  1887,  XXXI,  341. 

6  Winslow,  J.  Mass.  Ass.  of  Bds.  Health,  Bost.,  XI,  133. 
'  Park,  J.  Bost.  Soc.  M.  Sc,  189c>-1900,  IV,  213. 

8  J.  Infect.  Dis.,  Chicago,  1904,  I,  660. 

9  Clark,  J.  Mass.  Ass.  Bds.  Health,  Bost.,  XI,  124. 

10  Smith  and  Swingle,  Science,  N.Y.,  1905,  n.  s.  XXI,  481. 
"  Wheeler,  J.  Med.  Research,  Bost.,  1906,  XV,  269. 


14  THE  SOURCES  AND  MODES  OF  INFECTION 

somewhat  as  they  do  in  the  water  from  which  the  ice  is 
obtained.  It  must  also  be  remembered,  when  considering 
the  possible  danger  from  ice,  that  the  experiments  of 
SedgAvick  and  Winslow  and  Clark  show  that  when  water 
freezes  90  per  cent  of  the  contained  bacteria  are  excluded 
from  the  ice. 

Typhoid  and  Oysters.  —  Herdman  and  Boyce  ^  found  that 
in  oysters  artificially  infected  typhoid  bacilli  could  be  re- 
covered up  to  the  tenth  day.  The  bacilli  did  not  increase 
in  the  oyster  but  probably  perished  in  the  intestine.  In 
clean  water  the  oysters  freed  themselves  from  typhoid  bacilli 
in  from  1  to  7  days. 

Gorham  ^  has  made  extensive  studies  of  the  contamina- 
tion of  oysters  in  Narragansett  Bay  which  is  considerably 
polluted  by  sewage.  No  attempt  has  been  made  to  isolate 
the  typhoid  bacillus  but  attention  has  been  devoted  to  B. 
coll.  It  has  been  found  that  while  there  is  not  much  sea- 
sonal variation  in  the  colon  content  of  the  water  there  is 
a  very  great  variation  in  the  colon  content  of  the  oysters 
which  are  quite  free  from  these  bacilli  during  winter 
weather.  The  same  phenomenon  has  been  noticed  by 
Pease  in  New  York  and  by  Freeman  in  Virginia.  Gorham 
believes  that  during  the  winter  the  oyster  assumes  a  con- 
dition approaching  hibernation  and  during  this  time  the 
ciliary  movement  ceases,  and  with  it  the  current  of  water 
over  the  gills,  and  feeding  stops.  No  water  is  taken  in 
from  the  outside  and  the  bacteria  in  the  oyster  are  grad- 
ually eliminated.  Is  it  not  safe  to  assume  that  the  oyster 
is  cciually  free  from  typhoid  bacilli  in  the  winter,  at  least 
in  the  northern  United  States? 

Field '  found  that  when  typhoid  bacilli  were  planted  in 
living  oysters  they  ra])idly  dicul  and  none  could  be  re- 
covered after  the  ninth  day.     Wluui  the  oysters  were  dead 

'  Ilonliiian  and  Boycc,  Ilrp.  Thompson  Yates  Lab.  1898-9,  I. 

2  (Jorliam.  Am.  J.  Pul..  Ilcallli,  1912,  II.  21. 

»  Field,  iMcxl.  Nc-w.s,  N.  Y.,  1904,  LXXXV,  571. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      15 

or  dying,  there  was  a  verj^  considerable  increase.  Klein  ^ 
found  that  in  oysters  kept  in  sea  water  typhoid  bacilli  would 
live  from  6  to  7  days,  but  if  kept  out  of  the  water,  for  1 1  days. 
In  other  shellfish  their  life  was  longer. 

T3rphoid  and  Milk.  —  Sterile  milk  serves  as  an  excellent 
culture  medium  for  the  typhoid  bacillus,  but  ordinary  market 
milk  is  not  favorable  for  its  growth,  owing  to  the  rapid  pro- 
duction of  lactic  acid.  Bassenge '  says  that  when  milk  has 
soured  to  the  extent  of  0.3°-0.4°  Soxhlet,  and  has  continued 
in  this  condition  for  24  hours,  the  bacilli  are  destroj'ed.  Neu- 
feld  ^  states  that  they  usually  disappear  from  ordinary  milk 
in  from  2  to  3  days.  Pfuhl  *  found  the  bacillus  persisting  in 
the  milk  for  13  days.  Rosenau  and  McCoy  have  studied 
this  question  and  reviewed  the  literature.^  They  find  that 
raw  milk,  when  first  drawn,  has  a  feeble  antiseptic  action, 
and  typhoid  and  dysentery  bacilli,  when  added  to  it,  decrease 
slightly  at  times,  but  within  48  hours  their  numbers  increase 
enormously.  Eyre  ®  also  states  that  the  typhoid  bacillus 
may  increase  in  milk  to  enormous  numbers,  but  as  the 
milk  he  experimented  with  was  drawn  under  careful  aseptic 
precautions,  it  is  quite  likely  that  his  findings  would  not 
obtain  in  ordinary  milk,  owing  to  the  hostile  influence  of 
lactic-acid  and  other  bacteria. 

If  typhoid  bacilli  increase  in  number  in  ordinary  market 
milk,  extensive  outbreaks  ought  to  be  expected  in  our  large 
American  cities,  where  the  milk  is  handled  by  large  dealers 
drawing  their  supply  from  many  producers  situated  at  long 
distances,  so  that  the  milk  is  from  48  to  72  hours  old  before 

*  Klein,  Tr.  Path.  Soc.  Lond.,  1905,  LVI,  23;  Med.  Press  &  Circ, 
1905,  LXXIX,  264. 

*  Bassenge,  Deutsche  med.  Wchnschr.,  1903,  XXIX,  675,  697. 

*  Neufeld,  Kolle  u.  Wassermann,  Handbuch  [etc.]  Jena,  1903,  II,  213. 

*  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  555. 
'  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull.  No.  41, 

449. 

"  Eyre,  J.  State  M.  Lond.,  1904,  XII,  728. 


16    THE  SOURCES  AND  MODES  OF  INFECTION 

it  reaches  the  consumer.  Any  dilution  ought  to  be  more 
than  balanced  by  the  alleged  increase  in  the  bacteria.  But 
nearly  all  of  the  American  milk  outbreaks  reported  in 
Bulletin  41  of  the  Hygienic  Laboratory  were  on  small 
routes  where  the  interval  between  infection  and  delivery  was 
short.  No  outbreaks  due  to  railroad  milk  were  reported 
from  Boston,  New  York,  Philadelphia,  Chicago,  Buffalo, 
Baltimore,  or  St.  Louis,  and  of  one  hundred  and  twenty- 
nine  outbreaks  in  American  cities  only  two  instances  were 
reported,  namely  in  Washington,  D.  C,  in  which  typhoid 
infection  was  brought  in  over  a  railroad. 

Boers,^  Bruck^  and  PfuhP  have  demonstrated  the  persist- 
ence of  typhoid  bacilli  in  butter  up  to  27  days,  but  few  if 
any  outbreaks  have  been  traced  to  this  article  of  food. 

Mayer*  states  that  paratyphoid  bacilli  will  retain  their 
vitality  in  dried  human  feces  for  a  year  and  a  half. 

No  bacteria  can  grow  except  in  the  presence  of  moisture, 
so  an  increase  of  typhoid  bacilli  on  clothing,  furniture,  wood- 
work, etc.,  is  not  to  be  looked  for.  The  duration  of  life  under 
such  conditions  is  sometimes  shorter  and  sometimes  longer 
than  it  is  in  the  presence  of  moisture.  This  will  be  discussed 
further  in  another  connection. 

It  must  be  confessed  that  the  experimental  evidence  relat- 
ing to  the  growth  and  vitality  of  typhoid  bacilli  outside  the 
body  is  by  no  means  conclusive.  The  evidence  seems  to  be, 
however,  that  they  rarely  if  ever  increase  in  numbers,  and  in 
most  instances  they  tend  to  die  off,  and  that  quite  rapidly, 
often  in  a  few  days,  or  even  hours. 

Epidemiological  Evidence.  Soil.  —  There  is  not  much 
epidomiological  evidence  that  typhoid  bacilli  retain  their 
vitality  outside  of  the  body  for  more  than  a  few  weeks  or 

'  Boers,  cited  in  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg. 
Lab.  Bull.  No.  41,  24. 

'  HriK-k,  Deutsche  nied.  Wchnschr.,  190.3,  XXIX,  460. 

'  I'fiilil,  Ztschr.  f.  IlyK-  u.  Infect ionskrankh.,  Leipz.,  1902,  XL,  555. 

*  Mayer,  Munch,  nied.  Wclmschr.,  1908,  LV,  2218. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY     17 

perhaps  occasionally  for  a  few  months,  and  there  seems  to 
be  no  such  evidence  of  their  increase,  except  sometimes  in 
milk.  Westcott  ^  reports  an  instance  where  a  well  continued 
infected  for  20  months.  It  was  claimed  that  the  conditions 
were  such  that  continuous  infection  could  not  have  taken 
place,  but  this  does  not  appear  to  have  been  the  fact. 
The  numerous  instances  given  in  the  Report  on  Typhoid 
Fever  in  the  Spanish  War^  as  showing  the  growi;h  of  typhoid 
bacilli  in  the  soil,  are  by  no  means  conclusive.  Infected 
soil  was  supposed  to  have  caused  outbreaks  in  various 
army  corps,  but  other  sources  could  not  be  in  any  case 
excluded,  and  the  chances  of  other  modes  of  infection  in 
an  army  are  very  great.  The  infection  was  supposed  to 
have  remained  many  months,  and  it  is  possible  that  it  may 
have  in  some  instances  done  so.  As  a  matter  of  fact  90  per 
cent  of  the  volunteer  regiments  in  the  Spanish  War  sooner 
or  later  became  infected  whether  encamped  on  a  polluted 
site  or  not.  Koch  ^  believed  from  epidemiological  as  well  as 
from  bacteriological  evidence  that  it  is  very  rare  for  an  out- 
break to  be  due  to  long  continued  soil  pollution,  and  that  the 
possibility  of  the  gro-svth  of  the  bacillus  outside  the  body  may 
be  neglected.  In  1902,  Koch  undertook  the  investigation  of 
the  typhoid  fever  which  had  prevailed  for  some  time  in  sev- 
eral villages  in  Trier.  As  a  result  of  his  labors,  every  typhoid 
case  and  typhoid  carrier  in  four  of  the  villages  was  isolated, 
and  the  outbreak  ceased,  showing  that  it  was  due  entirely  to 
contact  infection  and  not  to  soil  infection. 

Epidemiological  Evidence.  Water.  —  Numberless  out- 
breaks of  tj^^hoid  fever  have  been  traced  to  infected  waters. 
In  some  instances  the  pollution  of  rivers  is  continuous,  and 
the  cities  supplied  from  them  suffer  from  a  uniformly  high 

'  Westcott,  J.  State  M.  Lond.,  1899,  VII,  104. 

'  Abstr.  of  Rep.  on  the  Origin  and  Spread  of  Tj^phoid  Fever  in 
U.  S.  Military  Camps  during  the  Spanish  War  of  1898,  Wash..  1900, 
206-209. 

»  Koch,  Die  Bekampfung  des  Typhus,  Berl.,  1903,  14,  19. 


18         THE  SOURCES  AND   MODES  OF  INFECTION 

death  rate  from  this  disease.  In  most  instances  water  out- 
breaks are  of  an  explosive  character,  the  onset  is  sudden  and 
they  often  end  suddenly,  though  sometimes  the  decline  is 
gradual  owing  to  the  development  of  a  certain  number  of 
secondary  cases  due  to  contact  infection.  A  few  days'  or 
sometimes  a  single  day's  pollution  is  sufficient  to  account 
for  the  whole  outbreak.  Three  outbreaks  of  this  kind  have 
occurred  in  Providence,  and  in  one  instance  it  was  clearly 
traced  to  the  throwing  upon  the  banks  of  the  river  of  the 
excreta  from  an  infected  family.  The  Providence  watershed 
covers  about  ninety-six  square  miles,  and  had  upon  it  in  1900 
a  population  of  some  35,000,  a  large  part  in  villages  along  the 
banks,  but  some  scattered  in  hamlets  and  farms  over  the 
whole  area.  The  death  rate  from  typhoid  fever  in  Rhode 
Island  is  not  less  than  20  per  100,000  in  the  country  districts, 
which  means  seven  deaths  per  annum  on  the  watershed.  As 
the  fatality  is  not  over  10  per  cent,  there  must  be  seventy 
cases,  and  if  we  add  the  "  carriers,"  the  number  of  persons 
each  year  distributing  typhoid  bacilli  on  the  watershed  must 
be  at  least  one  hundred,  and  perhaps  v(>ry  much  greater.  It 
is  also  certain  that  disinfection  of  excreta  is  practiced  to  such 
a  slight  extent  as  to  accomplish  very  little.  The  fact  that 
for  years  the  city  has  had  no  outbreak  of  disease,  and  no 
excess  due  to  the  water,  as  is  shown  by  the  typhoid  death 
rate  which  for  several  years  has  varied  from  seven  to  twenty- 
six  per  one  hundred  thousand,  indicates  that  the  typhoid 
bacilli,  which  are  ])cing  continually  deposited  on  the  water- 
shed, fail  to  multiply.  Exactly  similar  conditions  prevaij  on 
the  watersh(>(ls  of  Pawtucket,  Newport,  Woonsocket,  Hart- 
ford and  New  Haven,  only  to  mention  those  cities  in  my 
neighborhood  with  wliicli  I  am  j^TSonally  familiar.  And  the 
general  testimony  of  all  ei)i(l(Mni()l()gists  is  that  municipal 
water  supplies  are  never  continuously  infected  unless  com- 
paratively fri'sji  excreta  from  typhoid-infected  persons  pass 
directly  and  coiiliiiuously  into  them.  Nevertheless  it  is  cer- 
tain that  typhoid  bacilli  nmst  be  continually  discharged  onto 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      19 

the  soil,  and  we  are  justified  in  considering  the  freedom  from 
infection  of  the  surface  waters  coming  from  such  areas  a 
strong  evidence  that  the  growth  of  the  typhoid  bacillus  out- 
side the  body  does  not  commonly  occur,  and  is  a  negligible 
factor  in  the  causation  of  the  disease. 

Cholera.  —  Early  investigators,  as  Nicati  and  Rietsch, 
working  with  sterilized  soil  and  water,  found  that  cholera 
spirilla  would  live  outside  the  body  sometimes  as  long  as  2 
months.  But  all  the  more  recent  workers  agree  that  under 
natural  conditions,  in  unsterihzed  materials,  the  life  of  the 
organism  is  quite  short.  Loesner^  recovered  the  germs  from 
dead  bodies,  which  had  been  artificially  injected,  as  late  as 
the  twenty-eighth  day.  Houston"  says  that  they  usually  die 
off  in  the  surface  layers  of  the  soil  in  12  days,  though  they 
may  be  kept  alive  longer  if  the  soil  is  watered  with  liquid 
manure.  Though  Heiser^  states  that  the  spirillum  was  found 
in  the  quiet  water  in  the  bends  of  the  Passig  river,  no  evi- 
dence was  presented  to  show  that  it  grew  there.  Gotschlich* 
states  that  the  spirillum  is  rarely  found  in  feces  for  more  than 
three  days,  and  quotes  Abel  and  Draer,  Claussen  and  Dun- 
bar, and  refers  to  Koch,  as  stating  that  it  dies  in  dirty  canal 
water  in  24  to  30  hours.  In  unsterihzed  milk  it  may  live 
from  1  to  2  days,  but  dies  as  soon  as  the  milk  becomes  sour. 
All  these  agree  that  there  is  not  the  slightest  evidence  that 
the  cholera  spirillum  can  increase  in  numbers  outside  of  the 
l)ody.  On  the  other  hand,  Emmerich  and  Gemiind''  claim 
that  it  does  increase  in  numbers  in  the  soil,  and  may  be  found 
for  two  and  one-half  months.    Paladino-Blanchni"  also  states 

1  Loesner,  Arb.  a.  d.  k.  Gsndhtsamte.  Berl.,  1896,  XII,  448. 

'  Houston,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1898-9,  XXVIII, 
413. 

'  Heiser,  Philippine  J.  Sci.  (Med.),  1908,  III,  92. 

*  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1904,  IV,  108. 

^  Emmerich  and  Gemiind,  Mimchen  med.  Wchnschr.,  1904,  LI,  1089, 
1157. 

"  Centralbl.  f.  Bakteriol.  [etc.],  I,  Abt.  Ref.,  Jena,  1905,  XXXVI,  53. 


20  THE  SOURCES  AND  MODES  OF  INFECTION 

that  it  may  grow  in  polluted  soil.  Koch^  says  that  it  grows 
only  in  the  human  body. 

Cholera  and  Soil.  —  There  is  certainly  a  great  deal  of  clin- 
ical evidence  that  it  does  not  increase  in  the  soil,  but  on  the 
contrary  speedily  dies  out.  The  epidemic  of  cholera  in 
Europe  in  1885  was  very  widespread  in  Italy  and  Spain. 
How  extensively  it  prevailed  and  what  a  great  number  of 
towns  and  villages  were  infected  are  well  shown  in  the  excel- 
lent report  prepared  by  Shakespeare.^  Nevertheless  by  the 
succeeding  year  it  had  entirely  disappeared  from  Spain,  and 
largely  from  Italy.  Turkey  had  a  similar  experience.^  We 
know  that  with  the  sanitary  conditions  prevailing  in  those 
countries  at  that  time  the  soil  must  have  been  infected  with 
cholera  in  countless  places.  But  cholera  rarely  recurred,  and 
when  it  did,  it  was  in  large  cities,  where,  the  most  probable 
explanation  is,  it  was  maintained  during  the  interval  by  mild 
unrecognized  cases  or  latent  infections.  The  extensive  epi- 
demic in  the  United  States  in  1873  was  not  followed  by  a 
recurrence  in  the  succeeding  year.  Not  only  is  epidemiologi- 
cal evidence  strongly  against  the  saprophytic  existence  of 
cholera  in  temperate  climates,  but  it  is  equall}^  so  for  tropical 
regions.  The  great  outbreak  in  the  Philippine  Islands  in 
1902-3  attacked  hundreds  of  villages,  and  soil  infection  was 
universal,  yet  the  disease  speedily  died  out  all  over  the  islands.^ 
In  1905  there  was  a  similar  experience. 

In  the  Philippine  Islands  during  the  latter  outbreak 
it  was  believed  that  the  cooked  food  offered  for  sale  in  the 
streets  was  a  frequent  vehicle  of  cholera  germs,  and  a  num- 
ber of  samples,  particularly  of  boiled  rice,  were  found  to  con- 
tain the  spirilla.^     The  rice  was  probably  contaminated  by  the 

'  Koch,  Die  BckJimpfung  des  Typhus,  Berlin,  1903,  14. 
'  Shakespeare,  Rep.  on  Cholera  in  Europe  and  India,  U.  S.  Gov. 
Print.  Off.,  Wash.,  1S90. 

«  Clemow,  Tr.  Epidemiol.  Soo.,  Lond.,  1904,  n.  s.,  XXIII,  223. 
*  Woodruff,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  1160. 
»  Maus,  Med.  News,  N.  Y.,  1902,  LXXXI,  318. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY     21 

hands  of  sellers  or  purchasers.    Whether  the  spirilla  increased 
in  numbers  is  not  known. 

Mediterranean  Fever.  —  Mediterranean  or  Malta  fever 
has  long  been  recognized  as  endemic  at  various  points  on  the 
shores  of  the  Mediterranean,  particularly  on  the  island  of 
Malta.  It  shows  all  the  characters  of  "  endemic  "  disease, 
being  confined  to  certain  areas  and  exhibiting  little  tendency 
to  pass  to  other  parts  of  the  world,  or  to  extend  by  contagion. 
The  micrococcus,  M.  melitensis,  which  is  its  cause,  was  dis- 
covered by  Bruce  in  1887  and  has  been  very  carefully  studied 
by  an  English  commission  acting  under  the  supervision  of 
the  Royal  Society.  This  commission,  as  have  independent 
observers,  has  given  much  study  to  the  vitality  of  the  spe- 
cific organism  of  the  disease  outside  of  the  body.  The  evi- 
dence seems  to  be  that  it  tends,  like  other  disease  germs,  to 
perish  when  removed  from  the  body  and  deprived  of  nourish- 
ment and  moisture  and  exposed  to  light  and  heat,  but  it  may 
retain  its  vitality  for  weeks  and  even  months  under  certain 
conditions,  behaving  in  this  respect  much  like  the  typhoid 
bacillus.^  No  direct  experiments  seem  to  have  been  made  to 
determine  whether  it  ever  maintains  a  saprophytic  existence 
in  the  soil,  but  its  habits  of  life  are  such  that  it  is  a  fair  in- 
ference *hat  it  can  rarely  do  so,  and  that  such  saprophytic 
growth,  if  it  ever  takes  place,  is  of  no  greater  practical  impor- 
tance than  is  the  saprophytic  growth  of  typhoid  germs.  The 
migrococcus  was  carefully  sought  for  in  water  and  in  dust, 
but  was  never  found. ^  The  disease  is  referred  to  in  this  con- 
nection because,  on  account  of  its  localization  and  slight 
apparent  contagiousness,  it  was  beUeved  by  many  medical 
men,  as  well  as  the  laity,  to  spring  from  the  soil.  Yet  the 
work  of  the  English  investigators  has  conclusively  shown 
that  the  chief  source  of  the  disease  is  the  herds  of  infected 
goats.  It  is  by  the  infected  milk  of  these  that  the  disease 
is  transmitted  to  human  beings.     It  is  barely  possible  that 

^  Report  of  Commission  of  Royal  Society,  1901,  Pts.  I  and  II. 
»  Bruce,  Nature,  Lond.,  1908,  LXXVIII,  40. 


22  THE  SOURCES  AND  MODES  OF  INFECTION 

the  fever  may  be  spread  to  some  extent  by  contact  with 
infected  urine  either  of  goats  or  of  men,  just  as  typhoid 
fever  frequently  extends  by  contact  infection,  but  the  fact 
that  tliousands  of  infected  men  have  been  invahded  home 
to  England  without  any  extension  of  the  disease  in  that 
country  would  indicate  that  such  occurrence  is  extremely 
rare. 

Bubonic  Plague.  —  The  germ  of  bubonic  plague  is  not  so 
resistant  as  is  that  of  typhoid  fever,  nor  yet  is  it  of  such  feeble 
vitality  as  that  of  cholera.  It  is  rather  susceptible  to  disin- 
fectants, to  high  temperature  and  to  drying,  but  in  a  moist 
condition,  particularly  at  low  or  moderate  temperatures,  may 
remain  alive  for  some  months.^  The  endemicity  of  the  dis- 
ease in  many  localities  has  led  some  to  assume  that  it  devel- 
ops in  the  soil,  but  the  most  careful  students  see  no  necessity 
for  assuming  soil  infection  to  account  for  its  diffusion,  and 
there  is  ample  positive  evidence  that  plague  is  derived  from 
other  sources.  Yet,  in  view  of  the  fact  that  soil  infection 
has  been  so  much  discussed,  it  is  rather  remarkable  that  so 
few  actual  experiments  have  been  made  to  test  the  theory. 
Perhaps  it  is  because  such  experiments  are  difficult  and 
those  who  are  most  competent  to  make  them  have  thought 
their  time  better  occupied  with  work  giving  better  promise 
of  positive  results.  Elliot "  found  that  soil  naturally  infected 
would  cause  the  disease  in  rats  after  an  interval  of  a  month, 
and  Watkins-Pitchford  ''  in  some  careful  experiments  found 
that  inoculated  soil  retained  its  virulence  for  four  weeks,  but 
not  for  five  weeks.  The  soil  was  not  sterilized.  Oladin  ^ 
found  the  bacillus  alive  in  unsterile  moist  earth  after  2 

*  Rosenau,  U.  S.  Pub.  Iloaltli  and  Mar.  Hasp.  Serv.  Hyg.  Lab. 
Bull.  No.  4,  1901.     See  also  Simpson,  A  Treatise  on  Plague. 

'  Elliot,  Lancet,  Lond.,  1905,  I,  1562. 

'  Watkins-Pit(!hford,  Rep.  Gov.  Bacteriologist,  Pietermaritzburg, 
lOO.-]  [Report  on  I'laguo,  31]. 

'  flladin,  Centralbl.  f.  Baktcriol.  [etc.],  I,  Abt.  Orig.,  Jena,  1898, 
XXIV,  588. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      23 

months,  and  Rosenau  ^  kept  it  alive  a  long  time  in  cool  moist 
garden  earth,  and  the  Indian  Plague  Commission,  1901,  did 
the  same  in  moist  sterile  cow  dung.  Other  experiments  by 
Mackie  and  Winter  in  Bombay,  cited  in  the  Journal  of  Hy- 
giene,^ were  with  grossly  infected  cow  dung  from  the  floor  of  a 
native  house.  No  pest  bacilli  were  recovered  by  culture  on 
inoculation  after  96  hours.  Further  careful  experiments  have 
been  made  by  the  Indian  Commission  of  1905.  Their  con- 
clusions are  as  follows: 

"Floors  of  cow  dung  grossly  contaminated  with  the  bacillus 
of  plague  remain  infective  for  48  hours ;  floors  of  a  sort  of  na- 
tive cement  for  24  hours,  the  infectivity  being  tested  in  each 
case  by  inoculation.  The  floors  were  infective  to  animals 
allowed  to  run  on  them  for  only  half  the  above  time." 

Thus  there  appears  to  be  no  bacteriological  evidence  that 
the  bacillus  of  plague  grows  outside  of  the  bodies  of  living 
animals,  and  a  great  deal  of  evidence  that  when  separated 
from  the  body  it  tends  to  die  off  more  or  less  rapidly  and  fre- 
quently very  rapidly.  The  Indian  Plague  Commission  con- 
siders that  reports  of  soil  infections  are  unworthy  of  credence 
unless  continuous  and  careful  observations  on  the  presence 
of  rats  and  fleas  have  been  made. 

Dysentery  Bacillus.  —  One  form  of  dysentery  is  caused  by 
a  bacillus  belonging  to  the  colon  group,  and  it  has  a  number 
of  subpvarieties.  It  is  not  quite  so  resistant  as  the  typhoid 
bacillus,  but  it  has  been  known  to  survive  all  winter  in  damp 
earth. ^  It  is  said  that  in  Japan  local  outbreaks  often  persist 
longer  than  do  outbreaks  of  cholera,  perhaps  due  to  the  higher 
resistance  of  the  germ.^     The  bacilli  appear  to  be  easily  de- 

^  Rosenau,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 
No.  4,  1901,  9. 

'  J.  Hyg.,  Cambridge,  1906,  VI,  511. 

'  Schmidt,  Centralbl.  f.  Bakteriol.  [etc.],  I,  Abt.  Orig.,  Jena,  1902, 
XXXI,  522. 

'  Eldridge,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Pub.  Health 
Rep.,  1901,  1. 


24         THE  SOURCES  AND  MODES  OF  INFECTION 

stroyed  by  other  bacteria,  for  they  can  rarely  be  found  in 
feces  after  two  days,^ 

Dysentery  Amebae.  —  One  form  of  tropical  dysentery  is 
caused  by  an  ameba,  a  protozoan,  not  a  bacterium. 

There  has  been  much  dispute  concerning  these  amebae, 
but  it  is  now,  however,  believed  by  the  best  observers  that 
Entameba  coli,  commonly  found  in  the  intestines,  and  else- 
where, is  a  harmless  parasite,  but  that  E.  histolytica  and 
E.  tetragena,  and  perhaps  E.  minuta  and  E.  nipponica,  are 
true  parasites  and  pathogenic.  Craig  -  in  recent  work 
shows  that  in  all  probability  the  amebae  which  cause  dis- 
ease in  man  do  not  grow  readily,  if  at  all,  outside  of  the 
body.  As  most  convincing  evidence  he  alleges  the  ina- 
bility to  grow  in  cultures  the  pathogenic  forms  in  regions 
where  there  are  no  saprophytic  forms  to  contaminate  the 
cultures  and  deceive  the  observer. 

Bacteria  of  Suppuration.  —  The  formation  of  pus  in 
wounds,  abscesses,  or  elsewhere,  is  practically  always  the 
result  of  infection  by  bacteria.  Many  varieties  of  bacteria 
may  cause  suppuration,  but  a  few  species  such  as  the  Micro- 
coccus aureus,  M.  albus  and  M.  citreus,  and  Streptococcus 
pyogenes,  are  by  far  the  most  common  cause  of  this  proc- 
ess. According  to  a  resume  given  by  Gotschlich^  they  are 
constantly  found  growing  in  the  skin  and  on  the  mucous 
surfaces.  References  are  of  course  given  in  his  article  to 
numerous  original  investigations,  but  among  more  recent  ob- 
servations may  be  mentioned  those  of  Rucdiger,*  Gordon^ 
and  Hess.^     These  bacteria  are  also  found  in  the  tonsils  and 

1  Kruse,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  370,  386. 

2  The  Parasitic  Amoebic  of  Man,  Phila.,  1911,  58. 

*  Gotschlich,  Kolle  and  Wasscrmann,  Handbuch  [etc.],  Jena,  1902, 
I,  147. 

*  Ruediger,  J.  Am.  M.  Ass.,  Chicago,  190G,  XLVII,  1172. 

'•  Gordon,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1904-5,  XXXIV, 
387. 

«  Hess,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena,  1907, 
XLIV,  1. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY     25 

lymph  glands,  apparently  remaining  latent  for  long  periods 
of  time,  i.e.,  not  causing  suppuration.  Bacteria  such  as  the 
above,  which  are  the  constant  parasites,  or  perhaps  rather 
commensals  of  man,  are  naturally  to  be  looked  for  in  the 
vicinity  of  man  and  on  the  surfaces  of  the  body,  on  clothing, 
utensils,  furniture;  and  the  dust  and  dirt  of  all  places  fre- 
quented by  human  beings  are  found  to  contain  more  or  less  of 
them.  They  may  also  be  found  in  polluted  waters.  But 
whether  under  natural  conditions  they  are  commonly  able 
to  maintain  a  saprophytic  existence  is  another  matter.  Judg- 
ing from  what  I  have  read  in  the  text-books  I  should  suppose 
that  the  pus  organisms  are  not  so  limited  as  to  the  conditions 
of  their  growth  as  are  most  disease-producing  bacteria.  They 
are  not  so  dependent  on  a  high  and  even  temperature  or  on 
the  composition  of  the  medium  on  which  they  grow.  I  should 
suppose  that  they  would  be  more  likely  to  maintain  a  sap- 
rophytic existence  than  most  other  pathogenic  organisms,  yet 
I  do  not  know  that  such  existence  for  them  has  ever  been 
demonstrated.  In  fact  Gotschlich^ygays  that  they  are  not 
saprophytes.  Bacillus  pyocyaneus  has,  however,  been  found, 
by  Gorham,  growing  in  a  heap  of  moist  rags  at  a  paper  mill. 
Diphtheria. —  Diphtheria  was  not  so  very  long  ago  believed 
to  be  a  "  filth  disease,"  that  is,  its  germs  were  supposed  to 
have  a  habitat  outside  of  the  body  in  various  forms  of  "  dirt." 
This  theory  was  common  during  my  medical-school  days,  and 
when  I  began  health-department  work  in  1884,  I  tried  to  fit 
the  facts  as  I  saw  them  to  this  theory.  But  they  did  not 
fit,  and  the  impression  continued  to  grow  that  diphtheria 
was  a  purely  contagious  disease.  The  life  habits  of  the  diph- 
theria bacillus  indicate  that  while  it  is  more  resistant  than 
some  other  disease-producing  organisms  next  to  be  men- 
tioned, and  somewhat  easier  to  cultivate,  it  is  very  unlikely 
that  it  is  able  to  propagate  itself  outside  of  the  body,  except 
at  times  in  milk.     Houston,'  while  he  does  not  consider  his 

*  Gotschlich,  Kolle  and  Wassermann,  Handbuch  [etc.],  Jena,  IV,  173. 
2  Houston,  Loc.  Gov.  Bd.  Rep.  of  Med.  Off.,  1898-9,  XXVIII,  413. 


26  THE  SOURCES  AND  MODES  OF  INFECTION 

experiments  conclusive,  believes  that  the  bacillus  of  diph- 
theria dies  off  very  quickly  in  unsterilized  soils  of  various 
kinds.  Graham-Smith^  cites  a  number  of  writers  concerning 
the  vitality  of  the  organism  in  water  and  milk.  According 
to  Seller  and  Stoutz,  it  multiplies  in  sterilized  water  for  a 
while,  but  Montefusco  and  D'Espine  and  Marignac  found 
no  evidence  of  multiplication  even  in  distilled  water,  and  in 
polluted  water  it  dies  in  6  days.  Schottelius  reported,  con- 
trary to  general  experience,  that  the  bacillus  multiplies  more 
rapidly  in  raw  than  in  sterile  milk,  while  Montefusco  found 
no  multiplication  in  raw  milk  after  3  days,  and  Rubinstein 
found  that  the  bacilli  died  in  24  hours.  Eyre  showed  that 
in  milk  drawn  in  as  sterile  a  condition  as  possible  the  diph- 
theria like  the  typhoid  bacillus  undergoes  rapid  multiplica- 
tion. Kersten,^  on  the  other  hand,  reports  that  diphtheria 
bacilli  will  persist  in  raw  milk  for  72  days,  and  though 
they  undergo  no  increase  at  first,  do  so  later.  Montefusco 
found  that  they  died  in  fresh  bread  in  24  hours.  Except  in 
fairly  fresh  milk  at  room  temperature,  it  is  unlikely  that  the 
bacilli  of  diphtheria  multiply  outside  of  the  body. 

Other  Diseases.  —  Tuberculosis,  pneumonia,  influenza, 
cercbro-spinal  meningitis,  gonorrhea  and  syphilis  are  caused 
by  organisms  which  are  difficult  to  cultivate,  and  I  think  all 
bacteriologists  agree  that  it  is  futile  to  seek  for  their  habitat 
outside  of  the  bodies  of  men  or  other  animals.  As  for  the 
protozoan  diseases,  such  as  malaria  and  sleeping  sickness, 
such  a  habitat  is  still  more  improbable.  It  is  only  recently, 
and  after  laborious  experiment,  that  any  of  this  class  of 
organisms  have  been  cultivated  in  the  laboratory.  That  they 
grow  outside  of  the  body  under  ordinary  conditions  is  in  the 
highest  degree  improbable.  There  is  one  protozoan,  however, 
the  dysentery  ameba,  which,  if  recent  observations  are  cor- 
rect, does  live  outside  of  the  body.    But  this  organism  belongs 

'  Nultall  and  Grahain-Sinitli,  The  Tiactoriology  of  Diphtheria,  Cam- 
bridge, 1X9S,  171. 

^  Kerstcn,  Arb.  a.  d.  k.  (jHiidhtsamte.,  Berl.,  1909,  XXX,  341. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY     27 

to  an  entirely  different  class  from  the  blood  parasites,  and 
while  the  facts  so  far  known  render  it  not  improbable  that 
the  ameba  does  grow  outside  of  the  body,  the  facts  in  regard 
to  blood  parasites  are  against  any  such  hypothesis. 

Summary  of  Laboratory  Evidence.  —  It  appears,  then,  that 
so  far  as  experimental  evidence  is  concerned  there  is  no  war- 
rant for  assuming  a  source  for  the  common  infectious  diseases 
outside  of  animal  bodies.  It  is  onlj^  with  extreme  difficulty 
that  a  few  of  the  blood  parasites  belonging  to  the  protozoa 
can  be  cultivated,  and  the  cultivation  of  many  bacterial 
forms  is  strictly  limited,  so  that  it  is  hardly  possible  to  ima- 
gine their  maintaining  a  saprophytic  existence.  It  is  true 
that  the  bacteria  of  typhoid  fever  and  perhaps  cholera,  dysen- 
tery, and  diphtheria  may  be  conceived  of  as  growing  outside 
of  the  body  under  natural  conditions,  but  such  growth,  if  it 
ever  occurs,  must  be  rare. 

Lack  of  Epidemiological  Evidence.  —  Nevertheless  during 
the  larger  part  of  the  nineteenth  century  it  was  common  to 
seek  such  an  outside  source  for  most  of  the  infectious  diseases. 
The  filth  theory  of  disease,  the  vogue  of  which  was  largely 
due  to  Chadwick,  JMurchison  and  Pettenkoffer,  assumed  that 
the  specific  poison  of  many  of  our  common  infectious  diseases, 
and  particularly  of  typhoid  fever  and  cholera,  developed  in 
a  contaminated  soil,  or  in  other  forms  of  filth.  There  was  at 
that  time  no  knowledge  of  the  micro-organisms  which  cause 
disease,  and  the  theories  of  the  origin  of  disease,  so  far  as 
they  had  any  basis  at  all,  depended  on  clinical  or  epidemio- 
logical evidence.  There  was,  it  is  true,  some  epidemiological 
evidence  for  believing  that  typhoid  fever  and  cholera  could 
develop  in  filth,  for  both  of  these  are  excrement-borne  dis- 
eases, and  it  was  difficult  to  decide  without  any  knowledge 
of  the  bacteria  which  cause  them  whether  they  developed 
in  filth  or  were  merely  transmitted  in  filth.  But  as  regards 
typhus  fever,  smallpox,  scarlet  fever,  measles,  diphtheria 
and  similar  diseases,  there  is  really  no  epidemiological  evi- 
dence to  suggest  that  they  develop  outside  of  the  body.    If 


28         THE  SOURCES  AND  MODES  OF  INFECTION 

a  disease  does  have  its  source  in  the  outer  world,  we  should 
expect  to  find  it  localized,  attached  to  a  definite  locality, 
endemic,  as  it  was  formerly  called.  The  somewhat  well-de- 
fined infected  area  we  should  expect  to  maintain  its  infection 
for  some  time,  and  we  should  expect  persons  coming  into  the 
area  to  become  infected.  But  if  we  watch  the  outbreaks, 
especially  the  smaller  outbreaks,  of  such  diseases  as  measles, 
smallpox,  scarlet  fever,  diphtheria,  etc.,  which  occur  in  dif- 
ferent sections  of  cities,  or  in  villages,  we  find  nothing  to 
indicate  place  infection.  A  "  pin  map  "  of  these  diseases  in 
a  city  shows  first  one  or  two  pins,  indicating  infected  houses, 
then  more  appearing  day  by  day  in  the  surrounding  section, 
until  there  are  ten  or  twenty  or  a  hundred  cases  within 
the  radius  of  a  block  or  a  few  blocks  or  half  a  mile.  The 
scattered  groups  of  houses  are  of  a  somewhat  circular  form, 
a  little  denser  nearer  the  center.  The  outbreak  lasts  a  few 
weeks,  or  two  or  three  months,  and  then  disappears,  only  to 
reappear  in  another  part  of  the  city.  In  village  outbreaks 
contagion  is  usually  more  clearly  traced.  The  importation 
of  the  disease  and  the  sequence  of  the  earlier  cases  are  often 
made  out.  The  outbreak  lasts  only  for  a  moderate  time,  and 
then  the  disease  disappears,  usually  not  to  return  for  a  con- 
siderable time,  often  for  years.  There  is  nothing  to  indicate 
soil  infection.  If  these  diseases  really  come  from  privy 
vaults,  sink  drains  and  garbage  heaps,  we  should  expect  a 
very  different  distribution  in  the  house  from  what  is  actually 
found.  The  ground  floor  is  not  oftener  infected  than  the 
upper  floor,  nor  (for  some  might  say  that  rising  currents  carry 
disease  germs  to  the  top  of  the  house)  the  upper  than  the 
lower.  J3ut  what  is  most  important,  when  one  family  in  a 
house  is  attacked  with  such  a  disease  as  diphtheria,  we  should 
expect  the  other  families  to  be  usually  attacked  also,  if  the 
disease  is  a  disease  of  locality.  But  in  Providence  statis- 
tics for  th(;  last  twenty  years  show  that  in  scarlet  fever  and 
diphtheria  in  only  about  seven  per  c(>nt  of  the  houses  does 
the  disease  extend  from  one  family  to  another.    In  most  of 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      29 

these  cases  of  extension,  direct  contact  between  members  of 
the  families  is  shown  to  have  taken  place. 

In  such  important  diseases  as  smallpox,  measles  and  scarlet 
fever,  the  germs  of  which  have  not  been  isolated,  as  well  as 
in  typhus  fever,  diphtheria  and  whooping  cough,  epidemio- 
logical evidence  of  an  extra-corporal  origin  is  entirely  lack- 
ing. Epidemiological  and  laboratory  evidence  are  against 
the  growth  of  disease  germs  outside  of  the  body  under 
ordinary  circumstances.  The  notion  still  common,  even 
among  physicians  and  health  officers,  that  these  infectious 
diseases  are  filth  diseases,  as  that  term  is  ordinarily  under- 
stood, is  absolutely  without  foundation. 

Typhoid  Fever  and  Cholera.  —  T^-phoid  fever  and  cholera 
not  infrequently  appear  in  small  contact  outbreaks  very 
similar  to  those  of  scarlet  fever  and  diphtheria,  but  being 
excrement-borne,  contact  infection  is  not  so  common  as  in 
the  latter,  while  infection  by  water  and  food  is  more  common. 
Some  outbreaks  of  typhoid  fever  may  undoubtedly  be  inter- 
preted as  due  to  soil  infection,  but  they  can  also  be  explained 
otherwise,  and  the  bacteriological  evidence  is  so  strongly 
against  the  soil  hypothesis  that  we  are  not  justified  at 
present  in  assuming  it.  There  is  no  evidence  that  cholera 
finds  a  habitat  in  the  soil  of  temperate  climates,  and  the 
most  careful  observers  in  the  tropics  are,  I  think,  agreed 
that  it  is  not  different  there.  The  same  is  true  of  bubonic 
plague. 

Yellow  Fever  and  Malaria.  —  There  is  a  class  of  diseases 
for  which  there  seemed,  at  one  time,  to  be  very  strong  evi- 
dence that  the  cause  which  produced  them  had  its  origin  out- 
side of  the  body.  I  refer  to  yellow  fever,  malaria,  sleeping 
sickness  and  the  blood-parasite  diseases  of  cattle.  Malaria 
is  one  of  the  best  defined,  oldest,  and  best  understood  of 
diseases.  I  suspect  that  for  twenty-five  hundred  years  what 
has  been  known  of  malaria  has  decidedly  colored  prevailing 
views  as  to  the  nature  and  source  of  many  other  infectious 
diseases.    Malaria  is  a  typical  endemic  disease.    Its  localiza- 


30  THE  SOURCES  AND   MODES  OF  INFECTION 

tion  can  scarcely  be  better  illustrated  than  in  my  own  neigh- 
borhood. During  the  latter  half  of  the  nineteenth  century 
the  southern  part  of  New  England  suffered  from  extensive 
outbreaks  of  malarial  disease.  The  whole  country  was  by  no 
means  afTected,  but  well-defined  limited  areas  of  infection  were 
to  be  noted  all  over  the  region,  and  in  different  portions  of 
some  of  the  cities.  Infection  in  many  of  these  persisted  from 
year  to  year.  People  moving  into  them  became  sick,  and 
malaria  was  escaped  by  moving  away.  Most  of  these  areas 
were  in  close  proximity  to  swampy  land  and  marshes,  others 
were  some  little  distance  removed,  but  usually  in  the  direc- 
tion of  the  prevailing  winds..  Thus  there  was  presented  a 
perfect  picture  of  place  infection.  We  were  justified,  in  the 
then  existing  state  of  knowledge,  in  assuming  that  the  mala- 
rial poison  developed  in  the  wet  and  marshy  places  which 
were  closely  connected  with  these  infected  spots.  We  now 
know  that  this  assumption  was  incorrect,  though  it  was  very 
near  the  truth,  and  that  the  germs  of  malaria  do  not 
develop  in  the  marshes,  but  that  the  mosquitoes  which 
carry  the  germs  from  one  person  to  another  do  breed 
there.  As  far  as  sanitation  was  concerned  the  error  was 
not  serious.  The  new  facts  have  simply  enabled  us  to 
work  more  economically,  by  determining  accurately  just 
what  wet  places  are  dangerous.  But  the  apparent  certainty 
that  the  malarial  virus  developed  outside  of  the  body  had 
enormous  influence  in  encouraging  the  belief  that  other 
disease  poisons  also  had  an  extraneous  origin.  The  history 
of  yellow  fever  is  somewhat  similar  to  that  of  malaria.  It  is 
eminently  a  place  disease.  So  are  sleeping  sickness  and  Texas 
cattle  fever  and  a  number  of  other  diseases.  All  of  this  group 
we  now  know  are  transmitted  by  insects,  and  it  is  the  insects 
which  have  an  extraneous  existence  and  not  the  parasite  of 
the  disease.  Th(>  mico-organisms  whicii  cause  these  diseases 
do  not  grow  outside  of  the  bodies  of  human  beings  or  other 
animals  which  serve  as  hosts,  or  of  the  insects  which  serve  as 
carriers. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      31 

Review  of  Evidence.  —  In  reviewing  this  subject  we  are 
forced  to  the  conclusion  that  while  it  is  possible  that  the 
antlirax  and  tetanus  bacilli  and  the  pus-forming  bacteria 
may  develop  in  the  soil,  there  is  no  evidence  that  they  com- 
monly do  so.  It  is  also  possible  that  the  typhoid  bacilli,  and 
to  a  still  less  extent  the  bacteria  of  cholera,  dysentery  and 
plague,  maintain  a  limited  saprophytic  existence,  but  this  is 
probably  very  unusual.  There  is  ample  epidemiological  evi- 
dence that  in  temperate  climates  such  a  source  for  these 
diseases  must  be  an  almost  infinitesimal  factor  in  their 
development.  Probably  the  diphtheria  bacillus  never  has  a 
saprophytic  growth  of  any  significance,  unless  possibly  very 
rarely  in  milk.  As  for  tuberculosis,  pneumonia,  influenza, 
cerebro-spinal  meningitis,  scarlet  fever,  typhus  fever,  small- 
pox, whooping  cough,  gonorrhea  and  syphilis,  malaria,  yellow 
fever  and  sleeping  sickness,  there  is  not  the  slightest  reason 
for  supposing  that  they  ever  develop  outside  of  the  bodies  of 
animals. 

Changes  in  Present  Theories  and  Practice.  —  If  these  facts 
are  correct — and  I  can  scarcely  believe  that  any  will  seriously 
contend  that  we  have  any  evidence  that  an  appreciable 
amount  of  our  common  infectious  diseases  arises  in  the  exter- 
nal world — prevailing  notions  as  to  the  sanitary  functions  of 
the  state  should  be  decidedly  modified.  The  laity  and  the  lay 
press  still  believe  that  most  of  the  infectious  diseases  have 
their  origin  outside  of  the  body,  in  filth,  or  if  admitting  con- 
tagion, attach  equal  importance  to  external  sources  of  infec- 
tion. And  even  very  many  health  officials  and  some  teachers 
and  writers  on  sanitation  hold  the  same  view.  Municipal 
sanitation  and  municipal  cleansing  are  still  synonymous 
terms  to  many  health  officers.  It  is  true  enough  that  two  or 
three  diseases,  as  typhoid  fever  and  cholera,  the  germs  of 
which  are  found  in  human  excrement,  have  markedly  dimin- 
ished as  a  result  of  improved  methods  of  excrement  disposal, 
or  because  of  the  introduction  of  water  supplies  uncontami- 
nated  with  human  excrement.    It  is  also  doubtless  true  that 


32         THE  SOURCES  AND  MODES  OF  INFECTION 

whatever  promotes  municipal  cleanliness  tends  to  promote 
personal  cleanliness,  and  real  personal  cleanliness,  as  we 
shall  see,  is  doubtless  an  important  factor  in  the  preven- 
tion of  contagion.  Intelligent  and  effective  control  of 
excreta  disposal,  of  the  mosquito  nuisance  in  certain  regions, 
of  the  rat  nuisance  in  the  presence  of  plague,  and  perhaps 
of  the  fly  nuisance,  are  of  great  importance  in  the  preven- 
tion of  certain  diseases.  In  the  northern  parts  of  the 
United  States  typhoid  fever  and  dysentery  and  perhaps 
diarrhea  are  the  only  diseases  likely  to  be  effected  by 
nuisance  inspection  and  only  when  it  is  directed  along  cer- 
tain lines.  Except  for  a  few  diseases  or  except  for  very 
indirect  effects,  the  cleansing  of  streets,  alleys,  and  back 
yards,  of  dwellings  and  stables,  the  regulation  of  offensive 
trades,  and  the  prevention  of  nuisances  generally,  have,  so 
far  as  we  can  see,  no  effect  on  the  general  health,  nor  any 
value  in  the  prevention  of  specific  diseases.  While  munici- 
pal improvements  such  as  the  above  are  desirable,  there 
is  little  more  real  reason  why  health  officials  should  work 
for  them  than  there  is  that  they  should  work  for  free 
transfers,  cheaper  commutation  tickets,  lower  prices  for  coal, 
less  shoddy  in  clothing  or  more  rubber  in  rubbers — all  good 
things  in  their  way  and  tending  towards  comfort  and  health. 


CHAPTER  II. 

CARRIERS   AND    MISSED    CASES. 

A  Recent  Discovery.  —  That  there  are  occasionally  seen 
mild  cases  of  the  infectious  diseases  difficult  or  impossible  to 
recognize,  has  long  been  known.  That  such  cases  are  rare 
has  always  been  generally  believed.  That  the  germs  of  dis- 
ease can  maintain  themselves  and  increase  in  number  in  a 
person  without  causing  any  symptoms  at  all,  was  until 
recently  scarcely  thought  possible,  and  the  idea  that  such 
latent  infections  are  extremely  common  would  have  been 
scouted  as  preposterous.  Even  to-day  the  facts  are  denied 
by  many  sanitary  officials,  and  there  are  comparatively  few 
who  recognize  the  frequency  with  which  mild  atypical  forms 
of  disease  and  healthy  "  carriers  "  of  germs  are  found,  or 
realize  the  tremendous  importance  which  such  cases  have  in 
the  spread  of  the  contagious  diseases.  Undoubtedly  the  most 
fruitful  medical  discovery  of  the  last  century,  and  perhaps  of 
all  time,  was  the  discovery  of  the  parasitic  nature  of  the 
infectious  diseases.  Probably  the  most  important  discovery 
bearing  on  preventive  medicine  since  the  demonstration  of  the 
bacterial  origin  of  disease,  is  that  disease  germs  frequently 
invade  the  body  without  causing  disease.  The  succeeding 
pages  will  be  devoted  to  a  consideration  of  some  of  the  data 
available  concerning  the  existence  of  mild  cases  and  carriers. 
The  term  ' '  carrier  "  is  applied  to  those  persons  in  whom  patho- 
genic micro-organisms  exist,  but  who,  nevertheless,  show  no 
symptoms.  Such  carriers  are  rarely  found  by  the  health  offi- 
cer, and  the  very  mild  cases  also  naturally  escape  notice  and 
are  hence  called  by  the  English  "  missed  cases,"  i.e.,  cases 

which  fail  of  recognition. 

33 


34  THE  SOURCES  AND  MODES  OF  INFECTION 

Typhoid  Fever  not  an  Intestinal  Disease.  —  Bateriolo- 

gists  and  pathologists  now  consider  typhoid  fever  essen- 
tially an  infection  of  the  blood,  rather  than  a  disease  of  the 
intestines.  Houston  ^  urged  this  view  in  his  report  of  a 
urinary  carrier  in  1899,  and  it  was  also  set  forth  by  Horton- 
Smith  in  1900.-  The  latter  considers  that  the  bacilli  proba- 
bly pass  through  the  intestinal  wall  without  causing  changes 
there  and  proliferate  in  the  mesenteric  glands,  whence  they 
pass  into  the  circulation.  Pyer's  patches  are  secondarily 
infected  from  the  blood  stream.  A  number  of  instances  are 
recorded  in  which  the  bacilli  pass  through  the  blood  into 
the  fetus,  causing  a  systemic  infection  but  without  intes- 
tinal lesions.  It  is  a  fact  that  in  adults  the  intestinal 
lesions  are  frequently  slight,  and  often  the  bacilli  are  few  in 
number  in  the  feces,  and  sometimes  they  cannot  be  found 
at  all.  Somple  and  Grcig  ^  report  a  case  of  typhoid  fever 
in  which  the  bacilli  were  found  in  the  blood  from  July  20th 
to  September  20th,  but  were  never  once  found  in  the  feces  or 
urine. ^  So  far  as  we  know,  the  typhoid  bacillus  may  enter 
the  lymph  and  blood  from  any  portion  of  the  alimentary 
canal,  and  Semple  and  Greig,  Lentz,  Forster,  Kayser  and 
others  believe  that  it  frequently  enters  through  the  tonsils; 
and  Pratt,  Peabody  and  Long  ^  say  that  there  is  no  more 
evidence  of  entrance  through  the  intestines  than  through 
the  tonsils.  Indeed,  Lentz "  says  that  he  has  shown,  by  the 
finding  of  bacilli  in  the  tonsils,  that  the  latter  may  be  the 
portal  of  infection.  He  states  that  tonsillitis  is  of  common 
and  early  occurrence  in  typhoid  fever  and  quotes  Drigalski 
as  finding  it  in  40  ])er  cent  of  all  cases. 

1  Houston,  Brit.  M.  J.,  Loiul.,  1S99,  I,  78. 

2  Horton-Sinitli,  Brit.  M.  J.,  Lond.,  1900,  I,  827. 

'  Semple  und  fircin,  ^c.  Memoirs,  Med.  and  San.  Dept.,  Gov.  of 
India,  190S,  X.XXII,  9. 

*  See  also  Opie  and  Bassett,  citiMl  by  Pratt,  Beahody  and  Long. 

"  Bratt,  I'eahody  and  Lonji,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX, 
84(». 

•  Lentz,  Brit.  M.  J.,  Lond.,  1910,  II,  1501. 


CARRIERS  AND  MISSED  CASES  35 

In  any  event,  the  bacillus  is  soon  found  in  the  blood, 
and  continues  in  this  fluid  through  the  acute  stages  of  the 
disease.  Typhoid  fever  is,  then,  essentially  a  bacteremia, 
Audibert  ^  has  recently  shown  that  this  at  times  presents  a 
subacute  type.  The  bacillus  may  migrate  from  the  blood 
to  any  organ.  As  has  been  shown  by  Pratt,  Peabody  and 
Long,  a  favorite  habitat  is  the  gall  bladder.  Pratt  found  it 
in  the  gall  bladder  in  21  out  of  30  cases.  Kelly  ^  says  that 
typhoid  bacilli  were  found  in  7  of  74  gall-bladder  opera- 
tions, and  he  states  that  in  many  cases  there  is  no  evidence 
of  intestinal  infection.  Primary  cholecystitis  has  also  been 
reported  by  many  others.  Recently  Elmer  ^  reports  a  case, 
occurring  in  a  small  milk  outbreak,  in  which  the  only  symp- 
toms were  cholecystitis.  The  distended  gall  bladder  was 
drained  with  immediate  relief  of  the  symptoms.  The 
bacillus  may  also  infect  the  bones,*  kidneys,^  ovaries  and 
cerebro-spinal  fluid. ^ 

It  would  appear  from  the  pathology  that  typhoid  infection 
deviating  from  the  intestinal  type  is  by  no  means  uncommon. 

Typhoid  Bacilli  in  the  Feces.  —  Typhoid  bacilli  were  first 
sought  for  and  found  in  the  feces,  and  it  was  then  thought 
that  they  freely  developed  in  the  intestinal  contents.  It 
is  now  believed  that,  while  some  of  the  bacilli  in  the  feces 
may  have  their  origin  in  the  intestine  itself  or  its  contents, 
the  greater  number  come  into  the  gut  with  the  bile.  It 
was  long  known  that  they  could  be  found  in  the  bile,  but 
the  importance  of  this  fact  and  the  relation  of  these  bac- 
teria to  the  gall  bladder  was  not  recognized  until  the  car- 
rier question  came  to  the  front.  From  the  evidence  fur- 
nished by  a  considerable  number  of  animal  experiments,  as 

^  Audibert,  Le  Processus  Eberthien,  Masson  et  cie,  Paris,  1911. 
2  Kelly,  Am.  J.  M.  Sc,  Phila.,  1906,  n.  s.,  CXXXII,  447,  744. 
s  Elmer,  Arch.  Pediat.,  N.  Y.,  1911,  XXVIII,  217. 
*  Sultan,  Deutsche  med.  Wchnschr.,  1894.  XX,  675. 
5  Greaves,  Brit.  M.  J.,  Lond.,  1907,  II,  75. 

"  Lavenson,  Univ.  Penn.  Med.  Bull.,  1908-9,  XXI,  55.  Silber- 
berg,  Berl.  klin.  Wchnschr.,  1908,  XLV,  1354. 


36 


THE  SOURCES  AND  MODES  OF  INFECTION 


well  as  by  pathological  studies  on  human  beings,  it  seems 
probable  that  the  bacilli  reach  the  gall  bladder  by  way  of 
the  blood  stream.  Once  there,  they  may  merely  lead  a  sap- 
rophytic existence,  increasing  to  enormous  numbers  in  the 
bile  and  passing  with  it  into  the  intestine,  whence  they  are 
discharged  in  the  feces.  At  other  times  the  mucosa  of  the 
gall  bladder  is  attacked  and  becomes  inflamed,  and  nests 
of  bacilli  are  found  in  the  tissue.  Such  nests  are  not  con- 
fined to  the  gall  bladder  but  are  found  in  the  hepatic 
ducts,  which  fact  must  be  taken  into  account  when  it  is 
proposed  to  cure  intestinal  carriers  by  the  washing  out  or 
removal  of  the  gall  bladder.  Indeed,  Ledingham  refers  to 
cases  in  which  this  operation  did  not  prevent  the  subse- 
quent discharge  of  bacilli  in  the  feces. 

Loele  ^  opened  the  gall  bladder  in  a  convalescent  typhoid 
case  which  was  excreting  bacilli,  but  no  trace  of  them  could 
be  found  in  the  gall  bladder. 

Typhoid  bacilli  are  not  rarely  found  in  gallstones  and  it 
is  thought  by  some  that  they  make  their  way  into  the  stones 
after  they  are  formed,  but  the  general  opinion  is  that  they 
are  the  nuclei  around  which  the  stones  develop. 

The  bacilli  are  by  no  means  constant  in  the  intestines, 
even  during  the  course  of  the  disease,  and  indeed  they  are 
sometimes  entirely  absent,  as  in  Semple  and  Greig's  case 
previously  mentioned.  With  improvements  in  technique 
they  are  more  frequently  found  than  formerly.  The  fol- 
lowing figures  from  Gaehtgens  and  Briickner  in  1910  ^  give 
the  highest  percentages. 


Cases. 

Bacilli  found. 

Percentage. 

Ist  week 

21 

32 

13 

4 

2 

12 

17 

10 

2 

2 

57 

2nrl  week 

53 

3rd  week 

77 

4th  week 

50 

5th  week 

100 

»  Loele,  Deutsche  med.  Wchnschr.,  1909,  XXXV,  1429. 

»  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena,  1910,  LIII,  569. 


CARRIERS  AND  MISSED  CASES  37 

Typhoid  Bacilli  in  Urine.  —  Typhoid  bacilli  were  noted 
in  the  urine  as  early  as  1886  by  Hueppe,i  and  similar  find- 
ings were  reported  in  succeeding  years  by  many  other  ob- 
servers. The  first  extensive  study  of  this  condition  was 
made  by  Richardson  in  1898.^  The  bacilli  are  usually  not 
found  in  the  urine  until  the  later  stages  of  the  disease,  but 
are  occasionally  observed  earlier,  as  by  Connell,^  on  the 
seventh  day.  They  are  usually  in  large  numbers  and  often 
in  pure  culture.  Richardson  found  them  present  in  about 
23  per  cent  of  all  cases  examined,  and  earlier  and  later 
observers  give  about  the  same  figures.  Thus  Connell  tab- 
ulated 621  reported  examinations,  of  which  24  per  cent  were 
positive.  The  bacilli  generally  continue  in  the  urine  for 
a  while  after  recovery,  but  usually  disappear  within  three 
months.  Oftentimes  the  presence  of  the  bacillus  is  not 
accompanied  by  symptoms  referable  to  the  urinary  tract. 
Often,  however,  cystitis  develops,  which  may  persist  an 
indefinite  time,  accompanied  by  the  presence  of  the  bacilli 
in  the  urine.  The  pelvis  of  the  kidney  may  also  be  attacked 
by  the  bacilli,  and  foci  of  infection  may  be  found  in  the 
kidneys  themselves.  As  early  as  1889  Konzajeff  '*  reported 
finding  in  the  kidneys  infarctions  containing  typhoid  bacilli. 

Marchildon  ^  has  recently  reported  two  cases  in  which 
the  presence  of  typhoid  bacilli  in  the  urine  was  due  to  their 
growth  in  the  seminal  vesicles  and  the  prostate,  and  Gould 
and  Quails^  found  the  bacilli  in  the  prostatic  fluid  of  1  of  19 
convalescents. 

Typhoid  Bacilli  in  the  Sputum.  —  Pratt,  Peabody  and 
Long,  previously  quoted,  cite  several  observers  as  finding 

1  Hueppe,  Fortschr.  d.  Med.,  1886,  IV,  448. 

2  Richardson,  J.  Exper.  M.,  N.  Y.,  1898,  III,  349;   1899,  IV,  19. 

3  Connell,  Am.  J.  M.  Sc,  Phila.  and  N.  Y.,  1909,  n.  s.,  CXXXVII, 
637. 

*  Konzajeff,  Centralbl.  f.  Bakteriol.  [etc.],  Jena,  1889,  VI,  672. 

5  Marchildon,  Am.  J.  M.  Sc,  1910,  CXL,  74. 

«  Gould  and  Quails,  J.  Am.  M.  Ass.,  Chicago,  1912,  LVIII,  542. 


38  THE  SOURCES  AND   MODES   OF  INFECTION 

the  bacillus  in  the  bronchial  secretions  of  typhoid  fever 
patients,  and  state  that  Dieudonne  found  it  for  seven 
weeks  after  recovery.  Richardson  ^  also  reports  finding  it 
in  the  sputum  on  three  successive  days.  That  this  is  not 
a  common  condition  is  probable  from  the  investigations  of 
Tenney,^  who  examined  53  typhoid  fever  patients  without 
finding  the  bacilli  in  the  sputum.  A  few  of  the  cases  had 
bronchial  symptoms.  He  found  that  the  bacilli  would 
grow  and  survive  in  sputum  for  125  days. 

Typhoid  Carriers.  —  Though  typhoid  carriers  seem  to 
have  been  first  observed  in  England,  their  epidemiological 
importance  was  not  realized  until,  under  the  direction  of 
Koch,  the  active  campaign  against  the  disease  in  south- 
west Germany  was  begun  in  1903.  During  the  next  few 
years  extensive  observations  of  carriers  were  made  in  this 
and  other  portions  of  Germany. 

Since  the  first  edition  of  this  book  appeared,  J.  C.  G. 
Ledingham  ^  has  published  a  most  valuable  study  of  ty- 
phoid carriers,  and  in  addition  to  the  data  presented  in 
my  first  edition,  I  have  made  free  use  of  his  material  in  the 
following  pages. 

A  typhoid  "  carrier  "  is  a  person  without  signs  of  illness 
in  whom  typhoid  bacilli  are  living  and  increasing  in  num- 
bers. Some  of  these  carriers  have  had  typhoid  fever,  others 
so  far  as  can  be  learned  have  not.  In  a  large  proportion  of 
cases  the  carrier  condition  follows  convalescence  and  lasts 
only  for  a  few  weeks  or  months.  Some  cases,  on  the  other 
hand,  become  chronic  carriers.  Again,  persons  may  be  car- 
riers for  a  period,  perhaps  usually  short,  before  the  disease 
develops.  Various  names  have  been  applied  to  the  differ- 
ent kinds  of  carriers,  V)oth  by  the  Germans  and  by  the 
French,  and  a  formal  classification  has  ])ecn  suggested.     In 

1  Richardson,  J.  Bost.  Soc.  M.  Sc,  1897,  II,  21, 

2  Tcnnoy,  Bost.  M.  &  S.  J.,  1910,  CLXIII,  124. 

»  L(><lint,'h:iMi,  U(>i).  Mod.  Off.  Local  Gov.  Bd.,  Lond.,  1909-10, 
XXXIX,  249-384. 


CARRIERS  AND  MISSED  CASES  39 

Germany  carriers  who  excrete  bacilli  for  less  than  3  months 
are  generally  called  Bazillentrdger,  and  those  who  remain 
carriers  over  that  time  are  Dauertrdger.  The  English 
equivalents  are  "  temporary  "  or  "  transitory  "  carriers, 
and  "  chronic  "  carriers.  Sacquepee  ^  names  the  excretors 
of  bacilli  in  the  incubation  stage  as  "  precocious  "  carriers, 
those  who  have  had  the  disease  and  who  continue  to  ex- 
crete bacilli  for  less  than  3  months  as  "  convalescent " 
carriers,  those  who  excrete  them  over  three  months  as 
"  chronic  "  carriers,  and  those  who  have  never  been  sick  as 
"  healthy  carriers,"  or  "  well  carriers." 

For  the  present  purpose  interest  attaches  chiefly  to  the  fre- 
quency of  the  carrier  state,  the  length  of  time  it  continues 
and  the  liability  of  carriers  to  cause  disease  in  others.  Some 
carriers  excrete  bacilli  in  the  feces,  some  in  the  urine,  and 
some  in  both.     Only  one  sputum  carrier  has  been  reported. 

Carriers  during  Incubation.  —  Cler  and  Ferazzi,^  during 
a  food  outbreak,  found  6  of  39  persons  who  had  eaten  the 
food  and  who,  though  exhibiting  no  symptoms,  were  carry- 
ing the  bacilli  in  their  intestines.  These  "  precocious  " 
carriers  may  become  sick  later,  and  sometimes  the  period 
of  incubation,  so  called,  may  be  three  or  four  weeks,  or  even 
longer.^  Indeed,  it  is  not  rare  to  find  typhoid  bacilli  in  the 
feces  during  the  period  of  incubation.  Conradi  noticed 
this,  and  considers  it  an  important  factor  in  the  spread  of 
the  disease.^  Ravenel  and  Smith  ^  have  reported  an  out- 
break of  forty  cases  due  to  contact  with  a  case  before  the 
symptoms  had  developed.  Prigge  ^  discovered  3  carriers 
who  developed  the  disease,  18,  19  and  20  days  afterwards. 

»  Sacquepee,  Bull,  de  I'lnst.  Pasteur,  Paris,  1910,  VIII,  1,  49. 

*  Cler  and  Ferazzi,  Centralbl.  f.  Bakteriol.  [etc.],  Jena,  I  Abt.,  Ref. 
1905,  XXXVI,  479. 

>  Griffith,  Med.  Press  and  Circ,  1905,  LXXIX,  208. 

*  Conradi,  Deutsche  med.  Wchnschr.,  1907,  XXXIII,  1684. 

»  Ravenel  and  Smith,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1635. 
«  Prigge,  Klin.  Jahrb..  Jena,  1909,  XXII,  245. 


40  THE  SOURCES  AND  MODES  OF  INFECTION 

G.  Mayer  ^  reports  3  cases.  One  of  these  was  a  boy  whose 
stools  contained  the  bacilli  8  days  before  the  symptoms 
arose.  According  to  Ledingham,  Khnger  concluded  that  of 
812  cases  of  contact  infection  studied  by  him,  33  acquired 
the  disease  from  a  case  in  the  first  week  of  incubation  and 
150  during  the  second  week.  He  assumes  two  weeks  as 
the  average  period  of  incubation,  though  he  found  it  in  60 
cases,  in  which  its  duration  was  pretty  well  determined,  to 
vary  from  5  to  45  days,  the  average  being  16  days.  During 
the  Spanish  war  many  cases  of- typhoid  fever  were  attrib- 
uted to  exposure  to  cases  in  the  incubation  stage. ^ 

Convalescent  Carriers.  —  Drigalski  ^  was  the  first  to 
study  the  persistence  of  typhoid  bacilli  in  the  feces  of  con- 
valescents. Of  64  patients,  he  found  that  7,  or  11  per  cent, 
continued  to  excrete  them  from  8  to  10  weeks,  and  3  for 
over  3  months.  One  of  these  was  later,  at  9  months, 
found  to  be  still  a  carrier.  Klinger  *  at  Strassburg  examined 
482  cases  of  typhoid  fever  during  convalescence  and  63,  or 
13.1  per  cent,  were  carriers,  of  whom  8,  or  1.7  per  cent,  con- 
tinued so  for  a  period  of  over  6  weeks.  Later  ^  he  reported 
that  of  604  convalescents,  80,  or  13.2  per  cent  were  tempo- 
rary carriers,  70  intestinal  and  10  urinary.  G.  Mayer  ^ 
found  that  232,  or  24.9  per  cent,  of  930  typhoid  fever  cases 
became  carriers  during  convalescence.  Graham,  Over- 
lander  and  Dailey^  found  the  bacilli  in  the  feces  of  11,  or 
10.9  per  cent,  of  65  patients  after  defervescence  and  pre- 
vious to  their  discharge  from  the  hospital.     Including  the 

»  Mayer,  Centralbl.  f.  Bakteriol.  [etc.],  Jena,  I  Orig.,  1910,  LIII,  234. 

'  Abst.  of  Rep.  on  Origin  and  Spread  of  Typhoid  Fever  in  U.  S. 
Military  Camps  during  Spanish  War  of  1898,  Wash.,  1900,  178. 

»  Drigalski,  Centralhl.  f.  Bakteriol.  [etc.],  I  Abt.,  Jena,  1904, 
XXXV,  770. 

*  Klinger,  Arb.  a.  d.  k.  Gesundhtsamte.,  Berl.,  1900,  XXIV,  91. 
»  Klinger,  Arb.  a.  d.  k.  Gesundhtsamte.,  Berl.,  1907,  XXV,  214. 

•  Mayer,  Centralhl.  f.  Baklcriol.  [etc.],  Jena,  1  Abl.  Orig.,  1910, 
LIII,  2:{4. 

^  Graham,  Overlander  and  Dailey,  Bost.  M.  &  S.  J.,  1909,  CLX,  38. 


CARRIERS  AND  MISSED   CASES  41 

urinary  carriers  there  were  15,  or  23  per  cent.  Semple  and 
Greig  ^  report  that  16,  or  18.8  per  cent,  of  86  typhoid  con- 
valescents continued  to  excrete  bacilli  after  their  tempera- 
'fure  became  normal. 

Ledingham  ^  gives  a  table  and  chart  taken  from  Klin- 
ger's  account  (1909)  of  the  anti-typhoid  work  in  Germany, 
which  shows  the  age  and  sex  distribution  of  transitory  and 
chronic  carriers.  Of  211  of  the  temporary  carriers,  35 
were  between  5  and  10  years  of  age,  the  period  showing  the 
maximum  number  of  cases.  The  age  period  of  greatest 
incidence  for  the  220  chronic  carriers  was  between  40  and 
45,  at  which  period  there  were  30  cases.  Among  the  trans- 
itory carriers  the  proportion  of  females  to  males  was  1.4 
to  1,  while  among  the  chronic  carriers  it  was  nearly  5  to  1. 
Prigge  ^  shows  two  diagrams,  on  one  of  which  the  maximum 
age  of  female  cases  is  given  as  15  to  20  j^ears  and  the  aver- 
age age  of  female  carriers  as  40  to  45  years. 

Chronic  Carriers.  —  The  larger  number  of  convalescent 
carriers  cease  excreting  bacilli  at  varying  intervals  after 
their  recovery.  A  certain  number  remain  carriers  for  an 
indefinite  period,  sometimes  for  many  months,  sometimes 
for  years,  and  perhaps  occasionally  for  a  long  lifetime. 
The  earliest  and  most  extensive  series  of  observations  as  to 
the  number  of  typhoid  fever  patients  who  become  chronic 
carriers  was  made  by  the  men  carrying  on  the  campaign 
against  this  disease  in  Germany.  According  to  Ledingham, 
of  6708  typhoid  fever  cases  observed  during  the  years  1904 
to  1906,  166,  or  2.47  per  cent,  became  chronic  carriers.  Of 
3867  cases  in  1906  and  1907,  38,  or  1  per  cent,  proved  to 
be  chronic  carriers.  In  the  Bavarian  Pfalz  from  1904  to 
1907,  there  were  observed  930  cases,  of  which  78,  or  8.1  per 

^  Semple  and  Greig,  Scient.  Mem.,  Med.  and  Surg.  Dept.,  Gov.  of 
India,  1908,  XXXII,  9. 

2  Ledingham,    Rep.   Med.    Off.    Loc.    Gov.    Bd.,    Lond.,    1909-10, 
XXXIX,  267. 
.     3  Prigge,  KHn.  Jahrb.,  Jena,  1909-10,  XXII,  245. 


42         THE  SOURCES  AND  MODES  OF  INFECTION 

cent,  continued  to  excrete  bacilli  for  over  three  months. 
Park  ^  examined  the  feces  of  52  cases  eight  months  after 
recovery  and  found  bacilli  present  in  2;  in  one  of  them, 
however,  it  was  present  in  only  one  of  three  tests.  Of  16 
other  persons  who  had  the  disease  six  months  previously, 
2  were  carriers.  He  thinks  that  2  per  cent  of  all  typhoid 
fever  cases  became  permanent  carriers,  and  these  may  be 
found  in  the  population  at  the  rate  of  about  one  to  five  hun- 
dred. Bruckner  2  states  that  of  316  persons  who  had  the 
disease,  12,  or  3.8  per  cent,  became  carriers,  or  omitting  the 
104  children,  only  1  of  whom  was  a  carrier  and  who  rarely 
become  such,  5.2  per  cent  continued  to  excrete  bacilli. 
Semple  and  Greig,  before  referred  to,  found  nearly  4  per 
cent  of  typhoid  patients  remained  carriers  for  over  three 
months.  Aldridge,'  also  working  in  India,  reports  that  6 
of  190  convalescents,  or  3.1  per  cent,  remained  carriers  for 
longer  than  six  months.  Tsuzuki  *  found  3  of  51  convales- 
cents, or  5.8  per  cent,  to  be  chronic  carriers.  Recently 
Hamilton,^  following  out  the  suggestion  of  Gaehgtens,  tested 
the  opsonic  index  of  25  persons  who  had  gall-bladder 
trouble  and  found  7  with  an  abnormally  high  index.  All 
7  proved  to  be  carriers.  She  hopes  that  this  will  prove  a 
simple  means  of  discovering  carriers. 

In  Washington  ^  380  persons  Avho  had  had  typhoid  fever 
during  the  years  1904  to  1909  were  in  1909  examined  and 
8,  or  2.8  per  cent,  found  to  be  carriers. 

Klinger  found  that  of  220  chronic  carriers  30,  or  13.6  per 
cent,  had  gallstones.  There  is  no  doubt  that  the  presence 
of  typhoid  bacilli  in  the  bladder  and  gallstones  are  defi- 
nitely associated. 

»  Park,  J.  Am.  Ass.,  Chicago,  lOOS,  LI,  981. 

»  Bruckner,  Arb.  a.  d.  k.  Gesundhtsamto.,  Berl.,  1910,  XXXIII,  435. 

»  AhlridKo,  J.  Roy.  Army  Med.  Corpn,  Lond.,  1909,  XIII,  221. 

*  Tsuzuki,  Arch.  f.  Schiffs-u.  Tropen-IIyp;.,  Cassel,  1910,  XIV,  147. 
»  Hamilton,  .1.  Am.  M.  Ass.,  1910,  LIV,  704. 

•  U.  S.  Pub.  lleulth  and  Mar.  IIosp.  Serv.,  Hyg.  Lab.  Bull.  No.  77, 171. 


CARRIERS  AND  MISSED  CASES  43 

There  is  little  doubt  that  the  percentage  of  carriers  both 
convalescent  and  chronic  is  considerably  larger  than  is 
indicated  by  the  above  figures.  Owing  to  the  very  marked 
intermittency  with  which  bacilli  are  excreted  in  the  feces 
of  many  carriers,  an  intermittency  which  is  also  shown  by 
the  urinary  carriers,  though  to  a  lesser  extent,  it  is  certain 
that  more  extended  examination  of  the  excreta  would  dis- 
cover many  more  carriers.  It  must  be  remembered  that 
most  studies  of  this  subject  have  been  based  on  not  more 
than  two  or  three  examinations. 

Carriers  among  Contacts.  —  Persons  brought  into  inti- 
mate relation  with  the  sick  may  become  infected  without 
exhibiting  any  symptoms  whatever.  Drigalski  and  Con- 
radi  ^  found  the  infection  in  4  well  persons  in  contact  with 
typhoid  cases,  Liefmann  and  Nieter  ^  found  7  carriers  out 
of  252  persons  examined  in  an  insane  asylum,  some  of  whom 
it  was  believed  were  carriers  and  the  causes  of  the  out- 
break in  the  institution,  but  some  of  them,  however,  were 
true  contacts.  Scheller '  examined  40  persons  who  drank 
milk  which  had  been  handled  by  a  typhoid  carrier.  Of  these 
5  were  sick,  and  13  others,  who  had  no  symptoms,  were  yet 
found  to  be  excreting  typhoid  bacilli  in  either  feces  or  urine 
or  both.  All  of  them  became  free  from  germs  within  a  few 
weeks. 

Ledingham  states  that  at  the  St.  Brieuc  garrison  in  1909, 
Billet  and  others  found  1  carrier  among  53  men  who  lived 
in  rooms  where  the  cases  had  been  most  numerous. 

Tjrphoid  Bacilli  in  Persons  Never  Sick.  —  Not  only  are 
persons  who  have  had  typhoid  fever  found  to  be  "  carriers  " 
of  the  germs,  but  persons  who  have  never  had  the  disease, 
and  who   give  no   history   of   contact,   may  be  infected. 

*  Drigalski  and  Conradi,  Ztschr.  f.  Hyg.  u.  Infectionskrankh., 
Leipz.,  1902,  XXXIX,  283. 

2  Liefmann  and  Nieter,  Miinchen  med.  Wchnschr.,  1906,  LIII,  2097. 

»  Scheller,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena,  1908, 
LXVI,  385. 


44  THE  SOURCES  AND  MODES  OF  INFECTION 

Allowance  must,  however,  be  made  for  failure  to  recognize 
and  remember  mild  atypical  attacks,  and  some  of  the 
chronic  carriers  who  are  said  never  to  have  been  sick  may 
have  forgotten  an  attack  of  "  grip  "  or  "  malaria  "  years 
before.  Soper's  case  so  far  as  known  had  never  had  the 
disease.  Houston's  case,  which  had  the  bacilli  in  the  urine 
for  three  years,  had  not  been  sick.  One  of  the  carriers,  the 
source  of  several  cases,  discovered  by  Semple  and  Greig, 
had  never  had  typhoid  fever  so  far  as  known.  Roscoe  ^ 
reports  an  outbreak  of  twelve  cases  in  an  insane  asylum  due 
to  contact  with  a  carrier  who  had  never  had  the  disease. 
Jundell  2  notes  a  series  of  twenty-two  cases  on  an  estate 
in  Sweden  occurring  at  intervals  since  1854.  The  grand- 
mother of  the  family,  who  had  never  had  typhoid  fever,  was 
shown  to  be  excreting  the  bacilli  from  1904  until  the  time 
of  the  report,  1908.  According  to  Ledingham,  Prigge  found 
that  8  of  84  carriers  studied  by  him  had  never  had  the  dis- 
ease. Of  431  carriers  reported  by  Klinger,  163  gave  no 
history  of  having  had  typhoid  fever. 

Carriers  among  the  Public.  —  There  have  been  a  few 
studies  to  determine  the  number  of  carriers  in  the  general 
population.  Minelli  ^  found  1  carrier  in  250  prisoners  in 
Strassburg.  The  most  extensive  investigation  has  recently 
been  carried  on  in  Washington,^  where  the  feces  from  986 
well  persons  were  examined  bactcriologically.  Only  one 
test  was  made  for  each  person,  and  3  carriers  wore  found. 
These  were  subsequently  re-examined  and  two  proved  to  be 
negative. 

Much  more  evidence  is  needed  as  to  the  number  of  car- 
riers to  be  found,  both  among  the  general  public  and  among 

»  Roscoe,  Lancet,  Lond.,  1909,  II,  1137. 

2  Jundoll,  Abst.  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  388. 

'  Minelli,  Centralbl.  f.  Baktcriol.  [etc.],  Jona,  I  Abt.  Orig.,  1906, 
XLI,  400. 

*  U.  a.  Pub.  Health  and  Mar.  Hosp.  Scrv.,  Hyg.  Lab,  Bull.  No.  52, 
145. 


CARRIERS  AND  MISSED  CASES  45 

contacts.  Extensive  investigation  ought  to  be  made  in  dif- 
ferent parts  of  the  world  and  among  different  classes  of  people. 

Duration  of  Infection.  —  The  bacilli  may  be  found  in  the 
«rine  and  feces  of  carriers,  often  in  enormous  numbers,  for 
years.  Not  so  very  many  cases  have  been  followed  bacte- 
riologically  for  a  great  length  of  time,  though  in  one  in- 
stance the  positive  examinations  lasted  four  and  one-half 
years.  Tsuzuki  followed  several  cases  over  a  year.  Mayer, 
before  referred  to,  reports  the  following  duration  of  infec- 
tivity:  for  6  months,  56;  6  months  to  1  year,  38;  1  year 
to  2  years,  16;   2  years  to  4  years,  17. 

There  is,  however,  epidemiological  evidence  for  assuming 
a  much  longer  continuance  of  the  infection.  Dean  ^  reports 
the  case  of  a  medical  man  who  had  had  typhoid  fever 
twenty-nine  years  before,  and  had  since  then  frequent 
attacks  of  biliary  colic.  Typhoid  bacilli  were  recovered 
from  his  feces.  It  was  believed  that  no  one  had  contracted 
the  disease  from  him,  but  he  had  always  been  very  careful 
in  his  personal  habits.  Huggenberg  ^  noted  thirteen  cases 
in  a  household  extending  over  a  period  of  thirty-two  years. 
One  woman  who  had  the  disease  in  1877  was  shown  to  be 
a  carrier  in  1908.  Scheller  ^  reported  thirty-two  cases  ex- 
tending over  a  period  of  fourteen  years,  all  probably  due 
to  a  carrier  who  had  been  sick  seventeen  years  before. 
Gregg  ^  found  a  woman  whose  blood  gave  a  po.-itive  Widal 
reaction,  and  in  whose  feces  bacilli  were  found,  and  who 
had  had  typhoid  fever  fifty-two  years  before.  She  had 
presumably  infected  seven  persons.  Jundell's  case  reported 
above  was  infectious  perhaps  for  fifty-four  years.  Chal- 
mers' case  ^  had   had   the   disease   sixteen   years   before. 

»  Dean,  Brit.  M.  J.,  Lond.,  1908,  I,  562. 

2  Huggenberg,  Cor.-Bl.  f.  Schweiz.  Aerzte.,  1908,  XXXVIII,  622. 

3  Scheller,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena,  1908, 
LXVI,  385. 

,     ■«  Gregg,  Boston  M.  &  S.  J.,  1908,  CLIX,  80. 

»  Chalmers,  Rep.  of  Med.  Off.  Health,  Glasgow,  1907,  61. 


46         THE  SOURCES  AND  MODES  OF  INFECTION 

Frosch  ^  reports  that  evidence  was  presented  to  the  com- 
mission appointed  by  the  Prussian  Government  to  study 
this  subject  as  follows:  That  fourteen  carriers  had  been  in- 
fective four  to  nine  years,  six  for  ten  to  twenty  years,  and 
five  for  from  twenty-one  to  thirty  years.  Soper's  case  has 
now  been  infectious  for  ten  years,  and  a  number  of  other 
writers  report  instances  of  carriers  who  were  presumably 
excreting  bacilli  more  or  less  constantly  for  periods  of  from 
four  to  eight  years. 

Intermittent  Excretion.  —  From  what  has  been  said  about 
the  carrier  state  and  the  existence  of  nests  of  typhoid  bacilli 
in  the  tissue  of  the  gall  bladder,  the  hepatic  ducts  and  in  the 
tissues  of  the  urinary  tract,  it  might  be  surmised  that  ex- 
cretion of  bacilli  is  not  in  all  cases  continuous.  That  there 
have  been  reported  considerable  periods  in  which  the  feces 
and  urine  of  carriers  remain  free  from  bacilli  is  not  sur- 
prising. G.  Mayer  ^  claims  to  have  been  the  first  to  note 
this  intermittent  excretion  in  1905,  but  the  matter  did  not 
receive  much  consideration  until  Davies  and  Hall '  called 
attention  to  the  marked  intermittency  of  bacillus  excretion 
in  their  case,  reported  previously  by  Davies,  and  which  will 
be  again  referred  to.  This  patient  had  been  infectious  at 
times  for  four  years,  particularly  in  the  spring,  and  on  one 
occasion  she  was  herself  sick. 

Davies  and  Hall  laid  considerable  stress  on  this  presumed 
seasonal  intermittency,  ])ut  Ledingham,who  with  Thompson 
afterwards  followed  up  their  case  and  also  six  others,  con- 
siders that  the  evidence  is  not  convincing,  though  certainly 
their  carriers  gave  many  more  positives  during  the  first 
than  during  the  last  half  of  the  year.  Semple  and  Greig 
report  18  instructive  cases  which  they  followed  daily  for  a 
considerable  period.     One  of  their  cases  gave  only  negative 

1  Frosch,  Klin.  Jahrb,  Jona,  190S,  XIX,  537. 

2  Mayer,  Centrall)!.  f.  IJaktcriol.  [etc.],  I  Abt.  Orig.,  Jena,  1909- 
10,  LIII,  234. 

'  Davies  and  Hall,  Lancet,  Lontl.,  1908,  II,  1585. 


CARRIERS  AND  MISSED  CASES  47 

tests  for  thirty-one  days,  followed  by  a  positive,  another 
carrier  remained  free  from  bacilli,  as  shown  by  daily  exam- 
ination, for  a  period  of  seventy-five  days,  and  other  cases 
for  lesser  periods.  Scheller  noted  considerable  intermit- 
tency  in  the  excretion  of  bacilli.  Of  108  examinations  of 
urine  and  feces  from  18  carriers,  48  only  were  positive. 

Instances  of  marked  intermittency  have  been  noted  by 
others,  as  Briickner,  Kayser,  Nieter  &  Liefmann,  Eccard 
and  Prigge.  The  latter,  according  to  Ledingham,  noted 
intermittent  periods  lasting  from  one  to  two  and  one-half 
years.  Eccard,  in  an  effort  to  check  typhoid  fever  prevail- 
ing in  an  asylum,  discovered  three  carriers  who  were  effec- 
tually isolated.  The  disease,  however,  continued,  and  on 
three  subsequent  examinations,  made  several  months  apart, 
fresh  carriers  were  found  who  before  had  given  only  nega- 
tive results,  in  one  instance  five  times.  The  disease  ceased 
on  the  isolation  of  this  carrier.  This  experience  of  Eccard 
illustrates  how  greatly  intermittency  interferes  with  all  pre- 
ventive work  based  on  the  discovery  and  control  of  carriers. 
An  instructive  table  showing  the  marked  intermittency  of 
carriers  in  an  insane  asylum  is  given  by  Neisser.^ 

Carriers  Cause  Disease  by  Contact.  —  Perhaps  one  of 
the  most  convincing  instances  of  contact  infection  from  a 
carrier  is  the  cele'brated  case  of  "  Typhoid  Mary,"  so  well 
investigated  by  Soper.-  Between  August  27  and  Septem- 
ber 3,  1907,  6  cases  of  typhoid  fever  developed  in  a  banker's 
family  of  11  persons  at  Oyster  Bay.  All  the  usual  routes 
of  infection  were  most  carefully  investigated  by  Soper  and 
discarded  because  of  the  lack  of  evidence.  Convinced  that 
some  peculiar  event  must  have  occurred  in  the  family 
about  August  1,  he  sought  for  it,  and  the  only  change  that 
he  could  discover  was  a  change  in  cooks.  But  the  cook  had 
left  and  no  trace  of  her  could  at  the  time  be  found.  Soper 
concluded  that  she  was,  in  view  of  the  evidence,  the  most 

1  Neisser,  Bed.  klin.  Wchnschr.,  1910,  XLVII,  2142. 
*  Soper,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  2019. 


48  THE  SOURCES  AND  MODES  OF  INFECTION 

likely  source  of  the  trouble,  and  he  made  every  effort  to 
locate  her,  but  was  unsuccessful  until  she  had  figured  in 
two  more  outbreaks.  No  information  was  ever  obtained 
from  her  as  to  her  wanderings,  but  in  various  ways  Soper 
learned  that  a  case  developed  in  a  family  in  Mamaroneck 
where  she  lived  in  1900,  another  case  in  a  family  in  New 
York  in  1901,  7  in  a  family  of  9  persons  at  Dark  Harbor, 
Me.,  in  1902,  4  in  a  family  at  Sands  Point  in  1904,  and  7 
cases  at  Oyster  Bay  in  1906.  After  leaving  Oyster  Bay 
she  went  direct  to  Tuxedo,  N.  J.,  a  locality  free  from  ty- 
phoid fever  for  several  years,  but  where  the  laundress  de- 
veloped the  disease  fourteen  days  after  the  cook's  arrival. 
"  Mary  "  went  to  a  family  in  New  York  in  December  and 
within  a  few  weeks  2  cases  developed  in  this  family.  No 
wonder  that  with  this  evidence  extraordinary  means  were 
taken  to  obtain  specimens  of  her  excreta,  and  it  can  be  no 
surprise  to  any  epidemiologist  that  she  proved  to  be  a 
carrier.  She  was  confined  in  a  hospital  in  New  York  for  a 
long  time  and  her  release  was  refused  by  the  courts,  but 
she  was  after  a  while  discharged,  though  still  a  carrier,  and 
has  recently  brought  suit  against  the  city  for  150,000.  I 
am  inclined  to  the  opinion  that  few  even  of  the  scoffers  at 
the  "  carrier  theory  "  would  care  to  employ  Mary  Wallon 
as  cook. 

Hilgermann  ^  narrates  an  instance  in  which  new  servants 
coming  to  a  certain  house  soon  developed  typhoid  fever. 
Cases  were  reported  in  1895,  1900,  1902,  1903,  1905  and 
1907,  in  all  15  cases.  Suspicion  fell  upon  a  woman  of  71 
years  who  had  had  typhoid  fever  in  1894.  She  was  found 
to  be  a  carrier.  This  is  the  complement  of  Soper's  case, 
where  a  moving  carrier  infected  persons  in  successive  houses. 
Here  a  stationary  carrier  infected  a  scries  of  arrivals  at  her 
home.  G.  Mayer,  before  quoted,  shows  a  genealogical  tree 
of  195  cases  occurring  in  a  certain  district  in  Bavaria  during 
the  course  of  about  five  years.  In  this  tree  are  13  carriers, 
*  Hilgermann,  Klin.  Jahrb.,  Jena,  1908,  XIX,  463. 


CARRIERS  AND   MISSED  CASES  49 

and  from  8  of  them  the  disease  extended,  that  is,  without 
them  the  "  tree  "  would  have  had  many  less  branches. 
Of  these  13  carriers  2  had  a  recurrence  of  the  disease. 
During  the  years  in  which  his  observations  were  made,  of 
495  endemic  cases  of  typhoid  fever  160  were  traced  to  91 
carriers.  O.  Mayer  ^  has  traced  several  "contact  chains" 
from  carriers.  Sumacher,-  after  a  careful  investigation  in 
the  village  of  Crov,  reported  that  he  could  trace  26.6  per 
cent  of  the  cases  to  direct  contact  with  carriers  and  44.4 
per  cent  to  indirect  contact. 

The  following  case  came  under  my  o^vti  observation  in 
1911:  A  girl  15  years  old,  whom  we  will  call  A,  was  re- 
ported as  going  to  bed  with  typhoid,  March  3.  On  April 
12  the  family  went  to  their  farm  for  a  few  days,  and  again 
they  were  at  the  farm  on  April  29  and  30.  At  this  time 
two  friends  of  A,  Miss  B  and  Miss  C,  were  also  of  the 
party.  There  were  no  servants  at  the  farm  and  the  family 
prepared  the  food.  On  May  7  two  other  members  of  the 
family  were  taken  sick  with  typhoid  fever,  and  on  May  6 
Miss  C  went  to  bed  with  the  same  disease  and  on  May  9 
Miss  B.  On  May  17  the  father  came  down  with  typhoid 
fever,  and  a  few  days  later  the  mother.  The  evidence 
pointed  to  infection  at  the  farm,  and  of  course  the  family 
suspected  milk  and  water.  The  former  was  from  the  cow 
of  a  neighbor,  where  there  had  been  no  sickness,  and  the 
latter  was  found  to  be  excellent.  Further  evidence  acquit- 
ting the  farm  and  farmer's  famil}^  was  furnished  by  the  fact 
that  another  member  of  the  family,  a  student  at  Brjoi 
Mawr,  had  6  of  her  college  friends  at  the  farm  from  March 
22  to  April  2  and  none  of  them  developed  t^^phoid  fever. 
On  the  other  hand,  every  one  of  the  party  who  went  to  the 
farm  with  the  convalescent,  April  29-30,  later  had  the  dis- 
ease. The  city  milk  supply  was  beyond  suspicion.  I  nat- 
urally suspected  that  the  girl  A,  the  one  first  sick,  was  a 

1  Mayer,  Munclien.  med.  Wchnschr.,  1908,  LV,  1782. 
«  Sumacher,  Klin.  Jahrb.,  Jena,  1909-10,  XXII,  263. 


50    THE  SOURCES  AND  MODES  OF  INFECTION 

carrier,  and  had  infected  the  food  at  the  farm  on  April  29 
or  30,  thus  causing  the  sickness  of  her  brother  and  sister 
and  two  friends.  The  sickness  of  father  and  mother  might 
also  have  been  derived  from  A,  but  more  likely  from  the 
later  cases  which  they  helped  to  care  for.  No  examina- 
tions were  made  of  excreta  until  June  28,  when  A  was 
found  to  be  a  carrier,  as  I  at  first  suspected.  Typhoid 
bacilli  were  again  found  in  the  excreta  on  July  29. 

Davies  and  Hall  ^  report  the  case  of  a  cook  who,  after 
discharge  from  a  hospital,  where  she  had  had  typhoid  fever, 
went  to  her  home,  where  4  cases  developed  in  the  family. 
Besides  these,  4  other  cases  occurred  in  three  other  loca- 
tions;  in  all  8  cases  in  about  three  years. 

Carriers  Cause  Disease  in  Institutions.  —  Typhoid  fever 
not  infrequently  appears  in  institutions;  and  in  insane  asy- 
lums especially,  owing  to  the  difficulty  in  controlling  the 
habits  of  patients,  such  outbreaks  are  apt  to  occur.  Some- 
times the  source  is  to  be  found  in  a  sick  person  and  some- 
times in  a  carrier.  A.  &  J.  C.  G.  Ledingham  ^  report  an 
instructive  and  long-standing  institutional  infection  of  this 
kind.  The  asylum  in  1908  held  92  male  and  53  female 
patients.  Cases  of  typhoid  fever  had  developed  in  every 
year  between  1893  and  1907,  except  four.  In  all  there 
were  31  cases,  of  which  24  were  women.  Drainage  and 
water  supply  could  be  eliminated  as  causes.  All  of  the 
female  patients  were  examined  and  3  carriers  were  found. 
These  were  isolated  in  November,  1907,  and  since  then  no 
eases  of  the  disease  have  developed  in  the  institution. 

Ledingham  quotes  Eccard  in  regard  to  typhoid  fever  in 
a  large  asylum  at  Frankenthal.  Most  of  the  cases,  how- 
ever, occurred  in  a  female  block  containing  110  "  unclean, 
stupid  and  noisy  women."  From  1901  to  1906  there  had 
been  21  cases.     Repeated  search  for  carriers  was  made  in 

>  Rep.  Mod.  Off.  ITraltli,  Rrislol,  1000,  Gl. 

-  A.  tt  J.  C.  CJ.  Lcdiiiffluun,  lU-p.  Med.  Off.  Locul  Gov.  Bd.,  Lond., 

1000-10,  XXXIX,  ;ioi. 


CARRIERS  AND  MISSED  CASES  63 

1903  and  in  1906  and  1907.  In  the  latter  years  some  were 
discovered  whose  examination  in  earlier  years  had  been 
negative,  owing  probably  to  intermittent  excretion.  Since 
L906  no  cases  of  typhoid  fever  have  developed.  Other  in- 
stances of  asylum  typhoid  due  to  carriers  have  been  re- 
ported by  Liefmann  and  Nieter,  Levy  and  Kayser,  Friedel, 
Dehler/  C.  Neisser,^  Roscoe  ^  and  Ledingham.^  Dehler  ^ 
removed  the  gall  bladder  from  two  carriers  who  were  found 
to  be  the  cause  of  the  outbreak,  and  their  feces  were  after- 
wards free  from  bacilli. 

A  very  convincing  instance  of  carrier  infection  was  re- 
ported by  Davies  ^  of  Bristol,  England.  A  woman,  Mrs.  H, 
50  years  old,  had  had  typhoid  fever  in  1901.  In  May, 
1904,  she  went  to  a  home  for  girls  at  Brislington  to  work 
in  the  kitchen.  From  that  time  until  September,  26  per- 
sons in  the  institution  developed  typhoid  fever.  From 
September,  1904,  to  March,  1905,  Mrs.  H  was  in  private 
service.  She  was  then  cook  in  a  children's  home  for  some 
months.  The  one  case  which  developed  here  may  have 
had  no  significance.  In  April,  1906,  she  was  employed  in 
the  kitchen  of  the  Inebriate  Reformatory  in  Bristol.  In 
the  autumn  of  that  year  4  cases  developed  among  users  of 
institution  milk.  There  was  no  typhoid  fever  in  the  neigh- 
borhood, nor  had  there  been  any  in  the  institution  since  it 
was  opened.  There  was  another  outbreak  in  May,  1907, 
and  up  to  November  4  of  that  year  there  had  been  23 
cases.  Apparently  the  milk  was  at  fault,  and  if  so  was 
infected  after  sterilization.  Evidence  pointed  to  Mrs.  H, 
who  handled  the  milk  after  it  had  been  sterilized,  and  it 
was  discovered  by  Davies  that  she  was  a  carrier.  She  was 
then  removed  from  contact  with  the  food  and  there  were 

1  Dehler,  Munchen.  med.  Wchnschr.,  1907,  LIV,  779,  2134. 

*  C.  Neisser,  Psychiat.-neurol.  Wchnschr.,  Halle,  1908-9,  X,  37. 

*  Roscoe,  Lancet,  Lond.,  1909,  II,  1137. 

*  Ledingham,  Brit.  M.  J.,  Lond.,  1908,  I,  15. 

^  Davies,  Proc.  Roy.  Soc.  Med.,  1908,  I,  Epidemiol.  Sec,  175. 


52  THE  SOURCES  AND  MODES  OF  INFECTION 

no  more  cases.  Davies  and  Hall  ^  by  following  up  this 
case  showed  that  the  excretion  of  bacilli  was  markedly 
intermittent.  They  report  also  that  the  woman  had  what 
might  be  called  a  slight  relapse  in  May,  1908,  probably  a 
cholecystitis,  and  in  July  a  woman  with  whom  she  shared 
her  lunch  developed  typhoid  fever. 

Carriers  Cause  Disease  through  Milk.  —  In  typhoid  out- 
breaks due  to  milk,  water  or  food,  the  large  number  of 
cases,  massed  closely  together  in  point  of  time,  often  fur- 
nish far  more  certain  evidence  as  to  causation  than  do 
smaller  and  less  marked  outbreaks  due  to  contact  infec- 
tion. There  have  now  been  quite  a  number  of  milk  out- 
breaks reported  as  due  to  carriers,  and  some  of  these  are 
very  striking.  The  following  outbreak  was  reported  by  Lums- 
den  and  Woodward.-  Fifty-four  cases  of  typhoid  fever  were 
reported  on  the  routes  of  two  milk  dealers  in  Washington 
during  the  autumn  of  1909.  The  outbreak  was  localized 
in  that  part  of  Washington  still  known  as  Georgetown. 
This  section  of  the  city  was  served  by  about  thirty  milk 
dealers.  Of  the  54  patients,  33  took  milk  from  dealer  A 
and  21  from  dealer  B.  Dealer  A,  it  was  found,  received 
40  gallons  of  milk  daily  from  the  farm  of  Mrs.  X,  and 
dealer  B  received  20  gallons  daily  from  the  same  source. 
The  rest  of  Mrs.  X's  milk  was  peddled  direct  to  eleven 
families  nearby.  Among  these  were  3  cases,  not  seen  by  a 
physician,  which  quite  likely  also  were  typhoid  fever.  The 
age  distribution  of  the  cases  and  all  the  other  features  of 
the  outbreak  pointed  to  milk  infection,  with  its  source  on 
the  farm  of  Mrs.  X.  No  recognized  cases  of  typhoid  fever, 
or  illness  likely  to  be  mistaken  for  it,  had  occurred  on  the 
farm,  and  naturally  a  search  was  made  for  carriers.  Mrs. 
X  herself  was  found  to  be  excreting  typhoid  bacilli  in  her 
feces,  and  conditions  were  such  that  infection  of  the  milk 
from   her  was  very  possible.      If  a  well-defined   case  of 

1  Davies  ami  Hall,  Lancet,  Lond.,  1908,  II,  1,585. 

»  Lumsden  and  Woodward,  J.  Am.  M.  Ash.,  Chicago,  1909,  LII,  749. 


CARRIERS  AND  MISSED  CASES  53 

typhoid  fever  had  been  found  on  this  farm,  it  is  improb- 
able that  any  epidemiologist  would  for  a  moment  hesitate  to 
attribute  the  outbreak  to  that  case,  even  if  no  examination 
were  made  to  show  the  presence  of  the  bacilli  in  the  ex- 
creta. When  now  a  person  is  found  actually  discharging 
bacilli  in  large  numbers,  I  can  see  absolutely  no  reason  for 
not  considering  her  in  all  probability  the  source  of  the 
trouble.  The  fact  that  the  woman  had  typhoid  fever  as 
long  as  18  years  before,  and  had  not,  so  far  as  known,  previ- 
ously been  a  cause  of  disease,  is  urged  by  some  as  a  reason 
for  not  admitting  her  to  be  the  source  of  infection  at  this 
time.  We  know  in  the  first  place  that  many  carriers  are 
markedly  intermittent  in  the  excretion  of'^bacilli,  and,  what 
is  more  to  the  point,  it  is  by  no  means  as  easy  to  cause 
infection  of  persons  or  things  as  has  generally  been  be- 
lieved. Plenty  of  cases  of  typhoid  fever  have  occurred  on 
milk  farms  without  doing  harm,  and  numberless  cases  of 
scarlet  fever,  diphtheria  and  smallpox,  as  well  as  of  typhoid 
fever,  are  most  carelessly  cared  for,  yet  fail  entirely  to 
spread  disease. 

Bigelow  ^  reports  that  in  Worcester  in  1910  there  were 
mly  295  reported  cases  of  typhoid  fever.  Of  these,  204 
were  the  customers  of  a  single  dealer.  The  facts  pointed 
to  four  farms  as  possible  sources.  No  cases  of  the  disease 
were  found  on  the  farms,  and  blood  tests  gave  a  positive 
Widal  test  from  only  one  person,  who  daily  assisted  in  the 
milking.  He  had  had  typhoid  fever  26  years  before,  and 
about  two  weeks  before  the  outbreak  he  had  a  slight  attack 
of  diarrhea  with  a  little  blood  in  the  stools,  and  accompanied 
by  some  headache.  He  was  on  two  occasions  shown  to  be 
a  urinary  carrier. 

During  February,  1910,  there  was  an  outbreak  of  typhoid 

fever  in  New  York  City  in  a  section  corresponding  to  the 

route  of  a  large  milk  dealer.     Of  the  48  cases,  41  used  this 

milk.     The  infected  milk  was  traced  to  a  distant  farm  in 

1  Bigelow,  J.  Am.  M.  Ass.,  Chicago,  1911,  LVII,  1418. 


54  THE  SOURCES  AND  MODES  OF  INFECTION 

Vermont,  where  a  carrier  who  was  doubtless  the  source  of 
the  trouble  was  found.  It  is  worthy  of  note  that  a  labora- 
tory assistant  while  pipetting  a  culture  of  the  bacillus  from 
this  carrier  drew  some  of  it  into  her  mouth  and  two  weeks 
later  developed  a  typical  attack  of  typhoid  fever.' 

Bolduan  and  Noble  ^  report  an  outbreak  of  several  hun- 
dred cases  in  New  York  City  in  1909  which  was  traced  to 
that  portion  of  the  milk  of  a  large  dealer  which  came  from 
Camden,  N.  Y.  There  had  been  a  case  of  typhoid  con- 
nected with  a  creamery  there,  and  also  a  case  on  farm  X, 
the  milk  from  which  was  supposed  not  to  go  to  the  cream- 
ery, both  cases  becoming  sick  at  about  the  time  of  the  city 
cases.  But  it  was  found  that  farmer  X  did  send  a  part  of 
his  milk  to  the  creamery  and  thence  to  New  York.  It  was 
also  learned  that  there  had  been  much  typhoid  in  Camden 
for  several  years,  and  that  of  27  cases  in  1908-09,  20  were 
on  the  milk  route  of  X.  It  was  also  found  that  on  the 
farm  of  X  during  the  years  1878  to  1909  there  had  been 
7  cases  of  what  was  probably  typhoid  fever.  Mr.  X  him- 
self had  had  typhoid  fever  in  1863-64.  He  was,  on  two 
occasions,  a  month  apart,  found  to  have  typhoid  bacilli  in 
his  feces. 

The  Abundance  of  Evidence.  —  Only  a  very  few  though 
striking  instances  of  the  rise  of  sickness  from  carriers  have 
been  selected  for  the  purpose  of  illustration.  Within  the 
past  three  or  four  years  a  great  mass  of  similar  material  has 
appeared  in  the  medical  press, — material  already  too  abun- 
dant for  satisfactory  compilation.  Articles  are  constantly 
appearing  in  the  medical  journals  of  all  lands  reporting 
instances  of  apparent  infection  by  carriers.  It  is  true  that 
in  many  instances  the  evidence  is  by  no  means  conclusive, 
often,  indeed,  only  warranting  a  surmise.  In  many  cases,  on 
the  other  hand,  —  and  the  number  is  rapidly  increasing,  — 
the  evidence  which  leads  to  the  discovery  of  the  carrier  is 

»  Bolduan  and  Noble,  N.  York  M.  J.,  1911,  XCIV,  1313. 

»  Bolduan  and  Noble,  J.  Am.  Med.  Ass.,  Chicago,  1912,  LVIII,  7. 


CARRIERS  AND  MISSED  CASES  55 

as  good,  and  often  better,  than  that  on  which,  with  un- 
questioning confidence,  outbreaks  are  traced  to  recognized 
cases.  The  evidence  which  implicates  the  carrier  is  the 
same,  and  is  as  convincing  as  that  which  determines  the 
contagiousness  of  the  disease. 

Evidence  against  Carriers.  —  While  the  evidence  is  thus 
seen  to  be  very  strong  that  typhoid  carriers  are  an  impor- 
tant factor  in  the  spread  of  this  disease,  some  facts  are  pre- 
sented which  apparently  point  the  other  way.  Thus  Linos- 
sier^  says  that  at  least  10,000  persons  with  biliary  lithiasis 
must  visit  Vichy  each  year.  From  what  is  known  of  this 
condition,  it  seems  probable  that  a  large  proportion  of 
these  must  be  typhoid  carriers,  though  no  systematic  exam- 
inations have  been  made  to  determine  this.  If  this  is  so, 
typhoid  fever  ought  to  prevail  in  Vichy,  but  as  a  matter 
of  fact  there  is  very  little.  Linossier  explains  this  as 
perhaps  due  to  the  fact  that  most  visitors  to  Vichy  are 
beyond  the  age  of  marked  susceptibility  to  the  disease, 
and  in  part  also  because  they  are  mostly  well-to-do  and 
of  cleanly  habits. 

T.  Thomson  ^  also  finds  the  conditions  after  extensive 
water  outbreaks  somewhat  puzzling.  He  says  that  in 
Worthing  after  the  outbreak  of  1893,  in  which  8  per  cent 
of  the  population  of  17,000  were  attacked,  there  was,  for 
some  years,  less  typhoid  fever  than  before.  After  the  out- 
break in  Maidstone  in  1897,  involving  6  per  cent  of  33,000 
persons,  there  was  somewhat  more  typhoid  fever  for  about 
four  years;  and  in  Lincoln,  after  the  outbreak  in  which  2 
per  cent  of  52,000  persons  were  sick,  the  amount  of  typhoid 
fever  remained  about  the  same.  As  we  could  expect  the 
outbreaks  to  have  left  39,  57  and  30  chronic  carriers  in  the 
three  towns  respectively,  Thomson  says  that  one  would 
naturally  look  for  an  increase  in  the  disease  over  the  pre- 
epidemic  years.     Such,  however,  does  not  seem  to  have 

1  Linossier,  BuU.  Acad,  de  med.,  Par.,  1909,  3  S.  LXII,  627. 

»  Proc.  Roy.  Med.  Soc,  Lond.,  1910-11,  IV,  Epidemiol.  Sect.,  1. 


56  THE  SOURCES  AND  MODES  OF  INFECTION 

taken  place.  While  this  is  somewhat  paradoxical,  the 
problem  is  so  complicated  by  the  development  of  acquired 
immunity,  and  the  generally  falling  incidence  of  typhoid 
fever,  that  the  apparent  innocuousness  of  hypothetical  car- 
riers under  such  conditions  should  not  be  allowed  to  weigh 
too  heavily  against  the  very  clear  and  abundant  evidence 
on  the  other  side. 

Neisser  ^  calls  attention  to  the  danger  of  attributing  too 
much  importance  to  the  reports  from  certain  insane  asy- 
lums that  endemic  typhoid  fever  has  ceased  after  the  iso- 
lation of  carriers.  He  shows  that  in  other  institutions 
typhoid-free  years  have  occurred  without  any  control  of 
carriers.  He  also  states  that  in  four  institutions  where 
there  were  outbreaks  involving  79  cases,  21  attendants 
were  attacked,  while  of  the  attendants  on  carriers  he  can 
find  only  3  attacked.  He  considers  the  danger  from  car- 
riers less  than  is  generally  believed,  yet  he  thinks  it  suffi- 
cient to  warrant  the  examinations  of  all  newcomers  at 
Benzlau  and  their  isolation  under  the  care  of  immune 
attendants. 

Atypical  Typhoid  Fever.  —  There  can  be  no  question 
that  mild  unrecognized  cases  of  typhoid  fever  are  extremely 
common.  Greater  care  in  diagnosis  has  made  an  apparent 
increase  in  the  number  of  reported  cases  of  this  disease,  and 
a  decrease  in  fatality.  Thus  in  my  own  city  the  reported 
fatality  from  typhoid  fever  has  during  the  last  twenty 
years  been  reduced  from  50  to  12  per  cent;  and  it  is  prob- 
ably really  consideral)ly  less  than  that.  I  have  noticed 
that  in  milk  and  water  outbreaks,  when  public  attention 
is  directed  strongly  towards  the  disease,  the  case  fatality 
is  often  very  low,  which  merely  means  that  most  of  the 
cases  have  been  recognized.  In  the  Spanish  War  the  com- 
mittee of  investigation  believed  that  the  number  of  cases 
actually  existing  amounted  to  20,738,  while  the  number 
reported  by  the  army  surgeons  was  only  10,428. 

»  Neisser,  Berl.  kliii.  Wclinschr.,  1910,  XLVII,  2142. 


f-^ 


CARRIERS  AND  MISSED  CASES  57 

Recently  Bates  ^  has  reported  a  series  of  mild  atypical 
typhoid  fever  cases  in  Panama  Canal  Zone,  and  states  that 
such  cases  are  quite  common  there,  and  are  the  chief  factor 
m  the  extension  of  the  disease.  At  the  time  Koch  made  his 
investigation  of  the  four  Trier  villages  there  were  8  recog- 
nized cases,  but  a  thorough  bacteriological  investigation  of 
suspects  discovered  64  more.  Of  these  49  were  children.^ 
These  mild  unsuspected  walking  typhoid  cases  not  rarely 
result  in  death.  Velich  ^  notes  36  such  cases,  and  a  number 
of  others  are  reported  by  Curschmann,  and  they  also  have 
been  seen  by  the  writer.  I  have  recently  investigated  two 
milk  outbreaks,  in  one  of  which  the  cause  was  apparently 
a  mild  unrecognized  case,  and  in  the  other  either  a  con- 
valescent or  a  carrier  associated  with  him.  Neufeld  ^  de- 
votes considerable  space  to  this  class  of  cases. 

Lemoine^  for  three  years  examined  the  blood  of  every 
case^of  gastro-intestinal  disturbance  and  jaundice  in  his  ser- 
vice at  the  military  hospital  at  Val-de-Grace  and  found  ty- 
phoid bacilli  in  40  per  cent,  although  there  was  little  to  lead 
him  to  suspect  typhoid  fever.  Ledingham  quotes  Billet, 
etc.,  who  report  an  outbreak  of  typhoid  fever  of  142  cases 
in  a  regiment  at  St.  Brieuc.  Besides  these,  there  were  57 
other  atypical  cases  which  doubtless  would  not  have  been 
recognized  except  for  the  epidemic.  Bruckner  ^  reports 
three  outbreaks,  all  originating  in  mild  missed  cases.  He 
finds  that  children  are  very  susceptible,  the  most  suscep- 
tible age  being  11  to  15  years,  and  that  in  them  the  disease 
is  apt  to  run  an  atypical  course.  More  recently  ^  he  has 
reported  an  outbreak  in  an  institution  for  boys  in  which 

^  Bates,  J.  Am.  M.  Ass.,  Chicago,  1908,  L,  585. 

2  Koch,  Die  Bekumpfung  des  Typhus,  Berl.,  1893,  14-15. 

2  VeHch,  Arch.  f.  Hyg.,  Miinchen  u.  Leipz.,  1904,  XLIX,  113. 

*  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1903,  II,  271. 

«  Lemoine,  Presse  med..  Par.,  1910,  XVIII,  113. 

«  Bruckner,  Munchen  med.  Wchnschr.,  1910,  LVII,  1213. 

">  Bruckner,  Munchen.,  med.  Wchn.schr.,  1911,  LVIII,  1008. 


68  THE  SOURCES  AND  MODES  OF  INFECTION 

three-fourths  were  attacked,  many  cases  running  an  atyp- 
ical course  and  only  discovered  by  the  use  of  the  ther- 
mometer. Chamberlain  ^  says  that  a  third  of  all  cases 
among  both  American  and  Philippine  soldiers  can  only  be 
detected  by  laboratory  methods. 

The  Spanish  War  investigation  showed  that  most  of  the 
volunteer  regiments  were  infected  when  they  came  to  camp, 
that  is,  they  must  have  contained  carriers  or  mild  cases,  and 
it  was  by  extension  from  these  that  most  of  the  true  typhoid 
fever  later  developed.^  The  distinction  between  a  case  of 
true  typhoid  fever  of  mild  type  and  a  carrier  often  cannot  in 
practice  be  made.  There  is  no  sharp  line  of  demarcation, 
but  infection  by  typhoid  bacilli  may  result  in  a  series  of 
cases  presenting  gradation  from  the  most  severe  symptoms 
to  none  at  all.  It  is  most  unwarranted  to  assume,  as  some 
appear  to  do,  that  a  mild  unrecognized  walking  typhoid  case 
may  start  up  an  outbreak,  but  that  a  true  carrier  cannot 
do  so. 

Paratyphoid  Fever.  —  It  is  generally  admitted  that  ag- 
glutination does  not  afford  a  reliable  means  for  differenti- 
ating the  various  members  of  the  typhoid  group  of  bacilli. 
Recent  English  writers,  however,  as  Dean,  Bainbridge  and 
Firth,  believe  that  this  can  be  satisfactorily  accomplished  by 
means  of  complement  fixation.  According  to  Bainbridge,^ 
B.  suipestifer,  B.  enteritidis  (Gartner),  B.  partyphosus  A 
and  B.  paratyphosus  B  can  be  differentiated  in  this  way. 
The  first  two  of  the  above-mentioned  bacilli  are  connected 
with  disease  in  the  lower  animals  or  are  at  least  found  in 
such  animals  and  have  been  definitely  connected  with  out- 
breaks of  sickness  in  man  due  to  the  use  of  infected  food. 
B.  paratyphosus  A,  on  the  other  hand,  is  said  by  Bainbridge 

1  Chamberlain,  Philippine  J.  Sc,  1911,  VI,  Mod.,  299. 

'  Abst.  of  Rep.  on  the  Origin  and  Spread  of  Typhoid  Fever  during 
the  Spanish  War  of  1898,  Wash.,  1900,  168-175. 

'  Bainbridge,  Proc.  Roy,  Soc.  Med.,  Lond.,  1911,  IV,  Epidemiol. 
Sect.,  51;  Lancet,  Lond.,  1912,  I,  705. 


CARRIERS  AND  MISSED  CASES  59 

to  be  a  human  parasi-tc,  just  as  is  B.  typhosus  (the  ordi- 
nary typhoid  bacillus).  The  disease  caused  by  B.  paratypho- 
sus  ji  is  said  by  Firth  ^  to  be  very  common  in  India.  It  is 
iliilder  in  type,  with  a  more  irregular  fever  and  a  more 
sudden  onset,  and  is  accompanied  by  more  headache.  It 
may  very  frequently  be  recognized  clinically.  Grattan  and 
Wood  2  say  that  one-third  of  all  cases  of  uncertain  fever  are 
due  to  this  bacillus.  This  type  of  enteric  is  not,  according 
to  these  authors,  and  to  Bainbridge,  common  either  in  Eng- 
land or  the  United  States,  though  perhaps  its  apparent 
rarity  is  due  partly  to  lack  of  careful  investigation.  Grat- 
tan,' however,  could  not  find  this  bacillus  in  48  cases  of 
enteric  fever  studied  by  him  in  London.  But  in  India 
Grattan  and  Wood  studied  157  cases  of  this  disease.  Of 
these  10  became  carriers,  but  in  only  one  case  did  the  bacilli 
persist  for  as  long  as  5  months.  They  believe  that  these 
acute  carriers  are  a  greater  factor  in  the  spread  of  disease 
than  are  typhoid  carriers  in  ordinary  typhoid  fever. 
These  authors  *  report  an  outbreak  of  9  cases  of  this 
type  of  paratyphoid  fever  in  barracks  at  Benares,  prob- 
ably due  to  a  man  who  was  discovered  to  be  a  carrier. 
A  similar  outbreak  of  8  cases  due  to  a  carrier  was  reported 
by  Grattan. 5 

B.  Paratyphosus  B.  —  Bainbridge  and  O'Brien  ^  consider 
that  B.  paratyphosus  B  as  well  as  A  has  its  habitat  in 
man.  Carriers  are  frequently  found,  and  such  may  infect 
food  and  thus  cause  food  outbreaks  of  the  disease.  They 
did  not  find  this  bacillus  in  300  typhoid  convalescents,  but 

»  Firth,  Roy.  Army  Med.  Corps.,  Lond.,  1911,  XVII,  136. 

'  Grattan  and  Wood,  J.  Roy.  Army  Med.  Corps.,  Lond.,  1911, 
XVII,  143. 

»  Grattan,  J.  Roy.  Army  Med.  Corps.,  Lond.,  1910,  XIV,  385. 

*  J.  Roy.  Army  Med.  Corps.,  Lond.,  1911,  XXII,  131. 

8  Grattan,  J.  Roy.  Army  Med.  Corps,  Lond.,  1911,  XVI,  9, 

«  Bainbridge  and  O'Brien,  J.  Hyg.,  Cambridge,  1911,  XI,  68;  also 
Brit.  M.  J.,  Lond.,  1910,  II,  1503. 


60         THE  SOURCES  AND  MODES  OF  INFECTION 

they  did  find  it  in  6  cases  of  fever  in  which  it  was  appar- 
ently the  causative  agent,  also  in  4  convalescent  carriers 
and  in  3  healthy  persons.  According  to  Bainbridge,  car- 
riers of  B.  paratijphosus  B  were  first  noted  by  Lentz  and 
later  by  Hamilton,  Gaehtgens,  Bruckner,  Mayer  and  Prigge 
and  Sachs-Miike.  But  if  Bainbridge's  contention  is  cor- 
rect, and  if  these  Germans,  as  he  states,  have  not  made  use 
of  complement  fixation  to  differentiate  the  bacilli,  their 
data  cannot  be  relied  upon.  It  is  not  unlikely,  however, 
that  some  of  these  were  really  carriers  of  B.  paratyphosus  B. 
Of  those  noted  by  Prigge  and  Sachs-Miike,^  4  were  in  con- 
nection with  a  food-poisoning  outbreak.  One  of  the  car- 
riers was  under  observation  in  a  hospital  for  2  years. 
Another,  a  well  person,  was  found  to  be  a  carrier  during  a 
food-poisoning  outbreak,  and  6  months  later,  after  an  in- 
termission of  excretion  for  3  months,  finally  became  sick 
and  the  bacilli  were  found  in  the  feces. 

Bainbridge  and  Dudfield  ^  report  a  contact  outbreak  of 
13  cases  in  a  boarding  house  at  Paddington.  It  was  thought 
probable  that  iiii^was  due  to  a  carrier,  but  none  was  found. 
At  Wrexham  in  1910  over  100  cases  of  food  poisoning  oc- 
curred which  were  traced  to  pork  pies.  The  meat  was  not 
infected  when  received,  as  other  portions  sent  to  other 
places  did  no  harm.  Apparently  infection  took  place  dur- 
ing the  making  of  the  pies.  It  was  found  that  the  head 
cook,  who  did  not  eat  the  pies  and  who  was  not  sick,  had 
the  bacilli  in  the  feces  and  was  therefore  presumably  the 
carrier  who  infected  the  pies,  though  she  claimed  not  to 
have  had  anything  directly  to  do  with  the  making  of  the 
pies.  She  had  another  typhoid-like  bacillus  in  her  urine, 
and  these  too  were  found  in  the  pics.  Sacquepee  and 
Bellot '  also  report  the  case  of  a  cook  who  had  an  abortive 
attack  and  while  continuing  at  work  infected  19  persons  in 

»  Rachs-Miiko,  Klin.  Jahrb.,  Jena,  1909-10,  XXII,  237. 

2  Riinbri.lKo  an<l  Dudfield,  J.  HyR.,  Cambridge,  1911,  XI,  24. 

»  Sacqu(5pe6  and  Bellot,  Prog.  m6d..  Par.,  1910,  3.  s.  XXVI,  25. 


CARRIERS  AND  MISSED  CASES  61 

a  garrison  of  250.  G.  Mayer  ^  writes  of  a  man  who  became 
a  carrier  from  eating  meat  and  later  caused  the  infection 
of  another.  An  outbreak  of  38  cases  was  due  to  eating 
vegetables  fertilized  with  the  contents  of  a  privy  vault  used 
by  a  man  with  "  liver  trouble,"  who  had  paratyphoid  B 
bacilli  in  his  feces. 

Cholera  Spirilla  in  Convalescents.  —  Usually  the  germs 
of  cholera  disappear  from  the  feces  early  in  convalescence, 
and  until  recently  chronic  carriers  were  unknown.  Pfeiff er  ^ 
reviews  the  literature,  and  cites  Simond's  observation  that 
the  average  duration  of  infection  is  only  about  6  days,  and 
that  the  longest  seen  by  him  was  18  days.  Of  117  cases 
reported  to  Rumpel,  not  one  carried  the  germs  over  24 
days.  Abel  and  Claussen  found  the  average  of  17  cases  to 
be  5  or  6  days,  and  Pfeiffer  the  average  of  39  cases  10  days, 
though  in  2  the  infection  persisted  23  days.  Other  writers 
have  made  similar  observations. 

ZiroUa  ^  found  29  convalescents  excreting  bacilli  from  6 
to  40  days.  Zlatogoroff  ^  followed  255  cases  until  three 
negative  examinations  were  made.  In  134  the  spirilla  dis- 
appeared by  the  fourteenth  day,  and  in  22  they  persisted 
after  21  days,  in  one  case  lasting  for  56  days.  Burgers  ^ 
found  the  average  duration  of  infection  in  a  small  outbreak 
was  about  3  weeks  from  the  beginning  of  sickness,  but  in  one 
case  the  spirilla  persisted  for  69  days.  According  to  Kolle,^ 
cholera  spirilla  are  sometimes  found  in  the  intestines  of  con- 
valescents as  long  as  48  days.     Rommelaere '  reported  a 

1  G,  Mayer,  Centralbl.  f.  Bakteriol.  [etc.],  Jena,  I  Abt.  Orig.,  1910, 
LIU,  234. 

2  Pfeiffer,  Klin.  Jahrb.,  Jena,  1908,  XIX,  483. 
»  Abst.,  Med.  Officer,  1911,  VI,  84. 

*  Zlatogoroff,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena,  1911, 
XLVIII,  14. 

s  Burgers,  Hyg.  Rundschau,  Berl.,  1910,  XX,  169. 

^  Kolle,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1895,  XVIII. 

'  Rommelaere,  J.  de  med.,  Brux.,  1892,  XCIV,  837. 


62  THE  SOURCES  AND  MODES  OF  INFECTION 

case  retaining  the  infection  47  days.  Forrest  ^  found  the 
germs  remaining  6  weeks.  Kirchner  ^  says  that  the  spirilla 
are  sometimes  carried  for  weeks  or  months. 

Zlatogoroff  says  that  Jakowleff  found  the  germs  in  the 
feces  56  days  after  the  attack,  and  Zeidler  93  days.  Zlato- 
goroff  himself  found  them  for  56  days. 

Chronic  and  Intermittent  Carriers.  —  Until  recently  it 
was  thought  that  cholera  carriers  were  always  of  the 
"  temporary  "  type,  and  that  propagation  of  the  spirilla 
was  confined  to  the  intestinal  contents.  It  was  believed 
that  they  did  not  invade  the  gall  bladder  or  other  organs 
as  do  typhoid  bacilli.  Observations  by  Kulescha,  however, 
show  that  the  spirilla  can  be  found  in  the  gall  bladder  in 
10  per  cent  of  the  cases,  sometimes  producing  lesions  and 
propagating  in  the  biliary  passages.  Consequently  it  is 
not  surprising  that  Kulescha  reports  a  case  which  was  dis- 
charged from  the  hospital  in  January,  1909,  after  having 
had  the  spirilla  in  the  feces  for  57  days,  and  which  re-entered 
the  hospital  in  October  of  the  same  year  with  hepatic 
trouble  and  soon  died.  Cholera  germs  were  found  in  the 
biliary  passages.  McLaughlin,^  who  takes  these  facts  from 
Kulescha,  states  that  Gaffky  reports  a  cholera  convalescent 
who  was  a  carrier  for  6  months.  Adami,  Vallee  and  Mar- 
tineau  ^  have  published  notes  of  a  case  which  arrived  in 
Quebec  from  Russia  16  November,  1910.  The  man  had 
perhaps  had  a  slight  attack  of  cholera  on  the  steamship. 
At  any  rate  cholera  germs  were  found  in  his  feces,  and  he 
remained  a  carrier  until  the  next  May.  The  spirilla  were 
identified  by  agglutination. 

Intermittent  Excretion  of  Spirilla.  —  Intermittent  excre- 
tion, whi(!h  at  first  was  not  suspected,  is  now  known  to 
occur.     Zirolla  states  that  2  cases  observed  by  him  showed 

1  FoiTost,  J.  Trop.  M.  [otc],  Lond.,  1008,  XI,  321. 

2  Kircliiicr,  Klin.  Jiilirh.,  Jena,  1908,  XIX,  483. 

»  McLaughlin,  Boston  M.  &  S.  J.,  1911,  ChXY,  CAM. 

*  Adami,  Vall6e  and  Martincau,  Canad.  M.  Ass.  J.,  1910,  I,  697. 


CARRIERS  AND  MISSED  CASES  63 

a  germ-free  period  of  1  month  and  20  days  re.spectivel3\ 
During  such  a  period  attacks  of  indigestion  or  the  admin- 
istration of  salts  caused  the  spirilla  to  reappear  in  the  feces. 
Creel  ^  reports  the  case  of  a  carrier  under  observation  at 
quarantine  in  New  York  for  54  days.  Of  12  examinations 
of  the  feces,  6  were  positive  and  6  negative. 

Spirilla  in  Healthy  Persons.  —  Dunbar  ^  was  the  first  to 
note  the  occurrence  of  cholera  spirilla  in  the  feces  of  healthy 
persons.  He  discovered  28  healthy  carriers  in  Hamburg 
in  1892-93.  Rommelaere  noted  such  a  carrier  in  1892,  and 
carriers  are  by  Koch  considered  an  important  factor  in  the 
spread  of  the  disease.  In  1905  cholera  seemed  to  have 
been  brought  down  the  rivers  from  Russia  into  Germany 
by  raftsmen,  and  Kirchner  says  that  of  27  persons  on  one 
raft  2  were  carriers.  Pfeiffer  states  that  in  this  outbreak 
there  were  174  cases  of  the  disease,  and  that  38  other  car- 
riers were  discovered.  He  cites  Frosch  as  discovering  16 
carriers,  of  whom  12  were  children,  and  Friedheim  as  find- 
ing 51.  In  one  family  observed  by  Pfeiffer  4  died,  1  was 
very  sick,  1  was  mildly  sick,  and  2  were  carriers.  He  says 
that  there  are  very  many  mild  cases  of  the  disease  which 
can  only  be  recognized  bacteriologically.  Burgers^  dis- 
covered 6  carriers  connected  with  an  outbreak  of  30  cases 
in  East  Prussia.  In  Madeira  in  1910,^  of  600  contacts,  37 
proved  to  be  carriers.  Of  these,  12  later  developed  the  dis- 
ease. The  average  duration  of  infection  was  6  to  8  days. 
In  a  convalescent  it  continued  for  5  weeks.  McLaughlin^ 
found  17,  or  6.44  per  cent  of  264  prisoners  in  Manila,  to  be 
carriers,  and  in  the  city  27,  or  7.18  per  cent  of  376  persons 
examined. 

During  the  summer  of  1911  there  was  some  cholera  in 

1  Creel,  J.  Am.  M.  Ass.,  Chicago,  1912,  LVIII,  187. 

2  Dunbar,  Mod.  MecL,  Osier,  Phila.  &  N.  Y.,  1907,  II,  720. 
»  Burgers,  Hyg.  Rundschau,  Berl.,  1910,  XX,  169. 

*  Franca,  Bull.  Soc.  path,  exot.,  Par.,  1911,  IV,  358. 

s  McLaughhn,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1155. 


64  THE  SOURCES  AND  MODES  OF  INFECTION 

the  Philippines  but  only  1  case  in  Manila.  Of  7  persons 
brought  in  close  contact  with  this  case  all  were  shown  to 
be  carriers.^  While  during  an  outbreak,  as  stated  above, 
6  per  cent  of  the  population  may  be  found  to  be  carriers, 
McLaughlin  -  states  that  between  outbreaks  thousands  of 
stools  may  be  examined  without  finding  a  single  carrier. 
That  carriers  increase  as  the  number  of  cases  increase  is  a 
phenomenon  common  to  other  diseases  as  well  as  cholera. 
It  will  be  shown  in  the  following  pages  to  be  true  for 
cerebro-spinal  meningitis  and  for  diphtheria.  Jakowleff, 
Zabolotny,  Zlatogoroff  and  Kulescha  ^  state  that  in  St. 
Petersburg  the  feces  from  2440  apparently  well  persons 
were  examined,  all  of  whom  had  been  more  or  less  in  con- 
tact with  cholera  cases.  Of  these  125  showed  the  cholera 
spirillum,  of  whom  40  proved  to  be  mild  unrecognized 
cases,  25  were  incubating  the  disease,  and  60  were  true 
carriers. 

During  nearly  four  months  of  the  summer  of  1911,  while 
cholera  was  prevailing  in  certain  parts  of  Italy,  bacterio- 
logical examination  of  the  feces  of  immigrants  was  largely 
made  use  of  to  prevent  the  introduction  of  the  disease  into 
the  United  States.  A  sharp  watch  was  kept  by  the  steam- 
ship companies  and  by  the  United  States  officials  on  the 
other  side  to  prevent  the  embarkation  of  possibly  infected 
persons,  and  indeed  all  immigrants  from  infected  districts 
were  kept  under  observation  for  five  days.  Many  also 
were  subjected  to  bacteriological  examination.  According 
to  a  letter  from  Dr.  John  F.  Anderson,  of  about  20,000  so 
examined  in  Italy,  41  were  found  to  be  carriers.  Of  about 
25,000  immigrants  examined  at  American  ports,  27  were 
shown  to  be  carriers.     All  of  these  were  discovered  early 

1  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Pub.  Health  Rep.,  1911, 
1493. 

2  MfLaughlin,  N.  York  M.  .1.,  1011,  XCIII,  115. 

'  Jakowleff,  Zabolotny,  Zlatogoroff  and  Kulescha,  Bull.  See.  path, 
exot.,  Par.,  1909,  II,  276. 


CARRIERS  AND  MISSED  CASES  65 

in  the  season  while  the  control  of  embarkation  was  not 
so  strict. 

Gotschlich^  examined  pilgrims  returning  from  Mecca, 
§,]jd  though  cholera  had  not  so  far  as  known  prevailed 
among  them,  he  found  several  Russian  and  Turkish  pil- 
grims who  proved  to  be  carriers  of  the  spirilla.  Accord- 
ing to  Pfeiffer,  these  spirilla  of  Gotschlich  have  been 
carefully  studied  by  a  number  of  observers  and  show 
slight  variations  from  the  type,  and  have  probably  lost 
their  virulence. 

Atypical  Cases  of  Cholera.  —  While  perhaps  most  cases 
of  cholera  are  readily  recognized,  atypical  and  mild  cases 
occur,  and  they  are  particularly  frequent  among  children. 
McLaughlin  ^  says  that  cholera  in  children  simulates  acute 
and  chronic  enteritis  and  meningitis,  and  is  often  thus 
wrongly  diagnosed  by  practicing  physicians.  By  means  of 
examination  of  the  feces  he  raised  the  proportion  of  cholera 
cases  reported  among  children  from  22  to  35  per  cent  of 
the  total  cases. 

Cholera  Derived  from  Carriers.  —  Cholera  spirilla  from 
carriers  have  according  to  Zlatogoroff  and  others  been 
shown  to  be  as  virulent  for  animals  as  those  from  cases, 
but  this  perhaps  ought  not  to  be  taken  as  an  indication  of 
their  virulence  for  man.  While  Pfeiffer  gives  several  in- 
stances in  which  cholera  was  spread  by  carriers,  the  num- 
ber of  definite  cases  recorded  in  medical  literature  is  not 
large.  A  very  striking  one,  however,  is  reported  by  Mac- 
rae.^ In  a  hospital  in  Calcutta,  10  nurses,  3  patients  and 
a  sweeper  developed  cholera  within  4  days.  An  examina- 
tion of  127  articles  of  food  and  drink  demonstrated  spirilla 
in  14  samples  of  water  and  milk,  all  of  which  had  been 
handled  by  the  servants.     An  examination  of  12  servants 

'  Gotschlich,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1906, 
LIII,  281. 

2  McLaughlin,  Philippine  J.  Sc,  Manila,  1909,  IV,  Sec.  B,  363. 
»  Macrae,  Indian  M.  Gaz.,  Calcutta,  1909,  XLIV,  361. 


66    THE  SOURCES  AND  MODES  OF  INFECTION 

showed  that  2  were  carriers,  and  spirilla  were  recovered 
from  their  hands. 

Since  the  possibihty  of  the  spread  of  cholera  by  carriers 
has  been  recognized,  outbreaks  of  the  disease  have  occurred 
in  Russia  and  Germany,  and  both  Russian  and  German  ob- 
servers consider  that  carriers  afford  the  best  explanation 
of  many  of  the  phenomena  of  cholera  outbreaks.  The  re- 
peated occurrence  of  the  disease  in  the  Philippines,  since 
the  occupancy  of  the  islands  by  the  United  States,  has 
given  a  splendid  opportunity  for  the  study  of  cholera  epi- 
demiology, which  has  been  well  taken  advantage  of  by  our 
officials.  Heiser  and  McLaughlin  are  firmly  convinced  that 
carriers  are  a  most  important  factor  in  the  spread  of  the 
disease.  Indeed,  McLaughlin  says  that  their  importance 
can  hardly  be  overestimated.  He  has  no  doubt  that  chol- 
era is  often  spread  from  village  to  village  by  carriers,  and 
that  intervals  between  local  outbreaks  are  bridged  over  by 
the  same  means.  There  is  no  evidence  that  the  spirilla 
maintain  a  saprophytic  existence  in  the  soil  or  water  of  the 
islands. 

Chantemesse  ^  says  cholera  was  introduced  into  Italy  in 
1910  by  a  party  of  gypsies  who  arrived  at  Brindisi,  July  27, 
from  Batum.  They  then  went  to  Trani,  where  the  disease 
developed  August  7.  None  of  the  party  were  sick.  Cases 
developed  in  October  in  Marseilles  after  the  arrival  of  im- 
migrants from  the  East,  though  there  was  no  recognized 
sickness  among  them.  On  October  7  cholera  developed 
on  a  ship  which  carried  Russian  emigrants  from  South- 
ampton 30  days  after  the  latter  had  left  Russia.  The  bag- 
gage in  all  these  cases  had  been  disinfected  and  the  emi- 
grants themselves  had  been  examined  several  times  by 
physicians,  who  failed  to  find  recognizable  cholera. 

In  1911  there  were  five  cases  of  cholera  in  the  United 
States,  of  which  only  one  had  any  connection  with  a  pre- 
vious case.     Shall  we  assume  that  dried  and  dying  germs 
»  Chantemesse,  Bull.  Acad,  tie  tn6(l.,  Par.,  1911,  LXXV,  113. 


CARRIERS  AND  MISSED  CASES  67 

on  clothing  caused  them,  or  living  germs  from  a  carrier? 
In  1893,  at  a  time  when  a  cholera  ship  lay  in  the  harbor 
several  miles  from  New  York,  a  number  of  unconnected 
cases  occurred  in  that  city.  Were  they  caused  by  flies,  by 
floating  mattresses  or  clothing,  as  was  then  supposed,  or 
were  they  derived  from  a  carrier  from  some  other  ship? 
Similarly,  "  sporadic  "  cases  occurred  in  England  at  the 
same  period.  In  1873,  at  least  three  local  outbreaks  in  the 
United  States  were  traced  to  immigrants  recently  arrived 
from  Europe  at  points  in  the  interior.  Then  it  was  thought 
that  the  germs  were  brought  in  the  baggage.  To-day  do 
not  carriers  seem  a  more  likely  explanation?  In  1866, 
New  York  was  the  starting  place  of  an  extensive  epidemic. 
From  May  to  July  there  were  only  a  few  cases  in  the  city 
not  directly  connected  with  any  imported  cases,  nor  often 
with  each  other.  The  epidemiologists  of  the  day  attrib- 
uted these  cases  to  fomites,  or  the  feces  of  recovered  cases. 
Our  present-day  knowledge  shows  us  how  much  more 
likely  the  latter  is  as  a  cause  than  the  former,  and  vindi- 
cates the  judgment  of  the  men  of  that  day  who  without 
the  help  of  bacteriology  surmised  the  existence  of  the 
"  carrier."  McLaughlin  ^  says  that  in  the  Bilibid  prison  at 
Manila  the  food  and  water  were  so  well  controlled  that  the 
only  entrance  for  cholera  was  by  means  of  carriers.  As 
soon  as  carriers  were  sought  for  and  isolated  the  disease 
was  stamped  out. 

Bacillary  Dysentery.  —  There  are  two  forms  of  dysen- 
tery, one  caused  by  bacilli,  the  other  by  amebae.  The  dys- 
entery bacilli  form  a  group  of  closely  allied  types,  as  the 
Shiga,  the  Flexner  and  the  Harris  types.  Certain  of  the 
group  are  called  pseudo-dysenteric  but  yet  are  pathogenic. 
What  is  commonly  called  dysentery  may  be  caused  by  a 
number  of  different  pathogens,  and  the  dysentery  bacilli 
may  cause  diarrheal  symptoms  quite  different  from  typical 
dysentery.  For  the  present  purpose  the  whole  dysentery 
»  McLaughlin,  N.  York  M.  J.,  1911,  XCIII,  115. 


68  THE  SOURCES  AND   MODES  OF  INFECTION 

group  of  bacilli  may  be  referred  to  without  distinction. 
Collins  ^  and  Goodwin  ^  have  studied  the  occurrence  of  the 
bacillus  in  well  persons.  According  to  Collins,  Flexner, 
WoUstein  and  others  failed  to  find  it  in  healthy  persons. 
Duval  ^  found  it  in  2  instances,  and  Charlton  and  Jehle  * 
in  2  of  10  cases  examined.  Collins  found  it  in  2  of  30  normal 
persons,  and  in  1  three  weeks  after  an  attack  of  dysentery, 
and  in  another  child  who  had  had  a  few  mucous  stools. 
Goodwin  found  the  Flexner-Manila  type  of  the  bacillus  in 
1  of  59  well  persons  examined.  Kruse  ^  says  that  all  types 
of  the  bacilli  have  been  found  in  well  persons,  and  that  these 
carriers  are  an  important  cause  of  the  disease.  Though 
carriers  have  fewer  bacilli  in  their  feces,  which  are  also  less 
in  volume,  they  come  in  contact  with  a  larger  number  of 
persons  than  do  the  sick.  There  are  also  many  mild 
atypical  cases.  Kruse  has  found  the  bacilli  in  relapses 
after  two  years,^  and  says  that  Drjjgalski  and  Lentz  have 
made  similar  observations.  He  also  cites  Ford  as  finding 
10  carriers  among  50  persons  examined.  In  an  asylum 
outbreak  Heuser  ^  found  3  carriers.  Conradi,^  while  study- 
ing a  contact  outbreak  near  Metz,  found  several  carriers. 
Kiister  ^  isolated  bacilli  from  a  carrier  who  had  probably 
been  excreting  since  an  attack  years  before.  Kruse  cites 
Kricge  as  saying  that  about  4  of  36  cases  of  dysentery 
become  chronic,  but  usually  the  infection  lasts  only  2  to  6 
weeks.  Conradi  found  that  in  4  of  27  cases  the  bacilli 
persisted  up  to  the  end  of  the  fourth  week,  while  in  11 
cases  they  disappeared  by  the  middle  of  the  second  week. 

»  Collins,  Rep.  Dept.  Health,  City  of  Now  York,  1904,  I,  428. 

2  (Joodwin,  Rep.  Dept.  IlealMi,  City  of  New  York,  1904,  I,  423. 

»  Duval,  Studies  from  Rock(>feller  Inst.,  1904,  II,  42. 

<  Cliarlton  and  Jehle,  Tr.  Ass.  Am.  Physicians,  1904,  XIX,  405. 

"  Kruse,  Med.  Press  &  Circ,  1908,  LXXXV,  175. 

«  Kruse,  Klin.  Jahrb.,  Jena,  1908,  XIX,  529. 

7  Heuser,  Deutsche  med.  Wchnschr.,  1909,  XXXV,  1694. 

8  (Conradi,  I'Vstsehrift  v.  Rol)ert  Koeli,  1903,  555. 

»  Kuster,  Munchen  med.  Wchnschr.,  1908,  LV,  1833. 


CARRIERS  AND  MISSED  CASES  69 

Shiga  ^  says  that  the  bacilli  generally  remain  1  or  2  weeks, 
and  that  perfectly  normal  persons  sometimes  harbor  the 
germs.  Aveline,  Boycott  and  McDonald  ^  failed  to  j&nd  the 
bacillus  in  27  contacts  in  an  asylum. 

Cameron  ^  also,  and  Macalister,^  rarely  found  bacilli  in 
perfectly  healthy  contacts.  The  latter  writer  found  that 
26  per  cent  of  the  cases  studied  by  him  in  a  certain  asy- 
lum developed  a  mild  chronic  state  or  had  relapses,  and 
that  these  conditions  only  could  be  regarded  as  dangerous. 
These  he  considers  as  practically  carriers,  and  says  their 
importance  cannot  be  overestimated. 

0.  Mayer  ^  has  reported  finding  entirely  healthy  carriers, 
and  one  of  these  later  became  sick.  The  bacillus  found 
was  of  the  "  pseudo-  "  type  Y.  In  convalescents  he  found 
them  persisting  up  to  202  days.  The  average  persistence 
is  3  to  7  months.  In  healthy  persons  they  were  not  found 
over  30  days.  Intertriittency  of  excretion  was  noted  in 
both  convalescent  and  healthy  carriers. 

Chronic  Plague  in  Rats.  —  Bubonic  plague  is  a  disease 
which  attacks  not  man  alone  but  many  other  species  of 
animals,  particularly  the  rat.  In  fact  it  may  be  considered 
primarily  a  rat  disease,  and  without  doubt  the  rat  is  the 
most  important  agent  in  its  diffusion.  That  mild  cases 
and  chronic  cases  exist  among  rats  which  superficially  ap- 
pear not  to  be  sick,  seems  to  be  proved.  Simpson  ^  says 
chronic  plague  was  observed  in  some  of  the  animals  experi- 
mented on  in  Hong  Kong,  and  by  Albrecht  and  Ghon  in 
guinea  pigs,  and  in  rats  for  months  by  Kolle  and  Martini. 
The  Indian  Plague  Commission  (1905)^  found  eleven  of  the 

^  Shiga,  Philippine  J.  Sc,  Manila,  1906,  I,  485. 
2  Aveline,  Boycott  and  McDonald,  J.  Hyg.,  Cambridge,  1908,  VIII, 
309. 

»  Cameron,  Brit.  M.  J.,  Lond.,  1911,  I,  973. 

^  Macalister,  Brit.  M.  J.,  Lond.,  1910,  II,  1506. 

5  Mayer,  Miinch.  med.  Wchnschr.,  1910,  LVII,  2566. 

^  Simpson,  A  Treatise  on  Plague,  Cambridge,  1905,  129. 

»  J.  Hyg.,  Cambridge,  1907,  VII,  379. 


70  THE  SOURCES  AND  MODES  OF  INFECTION 

rats  which  they  had  fed  with  plague  bacilli  to  be  infected, 
although  they  appeared  to  be  perfectly  well.  While  chronic 
plague  has  been  seen  in  laboratory  animals,  several  observers 
in  Bombay  and  Sydney  have  failed  to  find  it  under  natural 
conditions,  as  also  did  Blue  in  San  Francisco.^  But  Hunter 
found  rats  with  chronic  plague  in  Hong  Kong,  and  the  In- 
dian Plague  Commission  (1905)  found  a  number  of  rats  in- 
fected with  plague  at  a  time  when  no  rats  with  acute  plague 
could  be  discovered,  and  when  there  was  no  outbreak  among 
human  beings.  The  infected  rats  showed  no  sign  of  sick- 
ness.^ Later  observations  discovered  similar  instances  of 
chronic  rat  infection  in  animals  caught  in  a  number  of  dif- 
ferent places.  The  pathological  conditions  indicated  a 
slowly  resolving  rather  than  a  true  chronic  process.  Wat- 
kins-Pitchford^  found  the  bacillus  in  convalescent  rats  and 
guinea  pigs.  It  is  evident  that  such  chronic  "  carriers  " 
may  be  an  important  factor  in  the  maintenance  and  exten- 
sion of  the  disease. 

Atypical  Human  Plague.  —  Among  human  beings  mild 
cases  of  the  glandular  type  are  by  no  means  uncommon. 
But  fortunately  these  are  rarely  dangerous,  for  without 
suppuration  there  is  no  escape  of  bacilli.  But  in  certain  in- 
stances, later  suppuration  may  take  place,  or  lung  symp- 
toms develop,  so  that  the  individual  may  become  a  focus  of 
infection.'*  Rat  "  carriers,"  on  the  other  hand,  are  always 
dangerous,  for  they  may  at  any  time  suffer  accidental  death, 
and  their  carcasses  may  then  readily  infect  other  animals 
and  even  man. 

Plague  Bacilli  in  Convalescents.  —  In  the  pneumonic  type 
ill  human  beings  the  bacilli  are  thrown  off  in  large  numbers 

•  Blue,  J.  Hyg.,  Cambridgo,  1909,  IX,  1. 

=  J.  llyg.,  Ciimbridgc,  1906,  VI,  530-535;    1907,  VII,  373. 
'  Watkins-Pitchford,  Rcj).  of  Bacteriologist,  Pictermaritzburg,  Natal, 
1903  [Ro.p.  on  Plague,  31]. 

*  (JoLschlich,  Kolle  u.  Wassermann,  Handbuch,  Jena  [etc.],  1904, 
IV',  09. 


CARRIERS  AND  MISSED  CASES  71 

from  the  lungs.  Martin/  Gotschlich  -  and  others  have  found 
them  in  the  sputum  up  to  76  days  after  the  attack,  or  42 
days  after  recovery.  Gaffky^  cites  Vagedes  as  reporting  pul- 
monary infection  lasting  2  months  in  a  case  in  Oporto,  and 
bacilli  in  an  abscess  persisting  more  than  2  months,  and  Vages 
one  lasting  4  weeks  in  Paraguay.  The  latter  also  isolated  the 
bacilli  from  a  man  who  later  became  sick  with  the  disease. 
Shottelius  found  the  germs  in  the  bronchial  secretion  of  mild 
ambulant  cases.  It  is  thus  very  probable  that  mild  cases 
and  true  carriers  among  both  rats  and  human  beings  may 
play  a  considerable  part  in  the  dissemination  of  this  disease. 
White  Diarrhea  of  Chicks.  —  One  form  of  diarrhea  com- 
mon among  young  chickens  appears  to  be  due  to  a  bacillus, 
B.  pullorum.  The  nature  and  mode  of  spread  of  this  dis- 
ease were  well  worked  out  by  Rettger  and  Stoneburn."*  It 
affects  young  chickens  three  or  four  days  old  and  spreads 
among  them  by  contact  or  infection  of  their  food  with 
excreta.  Many  of  the  survivors  become  carriers  of  the 
bacillus  until  after  they  have  become  mature  hens.  Such 
hens  show  few  or  no  symptoms.  The  eggs  which  these 
carriers  lay  become  infected  in  the  oviduct,  and  chicks 
hatched  from  them  develop  the  disease,  though  they  never 
come  in  contact  Avith  frank  cases.  Similar  observations 
have  been  made  by  Gage.^  Note  is  made  of  this  disease 
here  not  because  it  is  transmissible  to  human  beings,  for 
so  far  as  is  known  it  is  not,  but  because  it  is  an  excellent 
illustration  of  latency,  and  shows  how  efforts  to  suppress  a 
disease  are  doomed  to  failure  unless  account  is  taken  of  the 
part  played  by  carriers.  No  amount  of  isolation  of  chicks 
sick  with  this  form  of  diarrhea  can  ever  be  successful  in 
stamping  out  the  disease. 

1  Martin,  Ann.  de  I'lnst.  Pasteur,  Par.,-  1900. 

2  Gotschlich,  Ztschr.  f.  Hyg.  Infectionskrankh.,  Leipz.,  1899,  XXXII, 
402. 

3  Gaffky,  Klin.  Jahrb.,  Jena,  190S,  XIX,  491. 

*  Rettger  and  Stoneburn,  Storrs,  Agric.  Ex.  Sta.,  Bull.  60  and  68. 
5  Gage,  J.  Med.  Research,  Bost.,  1911,  n.  s.,  XIX,  491. 


72    THE  SOURCES  AND  MODES  OF  INFECTION 

It  is  also  interesting  to  note  the  analogy  to  ophthalmia 
neonotorum,  which  in  many  cases  is  due  to  mild,  long- 
standing and  unrecognized  infection  of  the  genital  tract  of 
the  mother  with  the  gonococcus. 

Mediterranean  Fever. — Mediterranean  fever,  like  plague, 
appears  to  be  a  disease  of  the  lower  animals,  only  secondarily 
affecting  man.  The  germ  which  is  its  cause  may,  like  so 
many  other  pathogenic  organisms,  develop  in  the  body  with- 
out giving  rise  to  symptoms.  Goats  appear  to  be  the  chief 
source  of  human  infection.  In  1905  there  were  3G3  cases 
among  the  garrison  at  Malta,  but  in  1906,  presumably  owing 
to  the  cutting  off  of  the  supply  of  goat  milk,  there  were  only 
35  cases;  ^  and  in  1907  it  was  practically  exterminated.-  An 
interesting  account  is  given  of  an  outbreak  of  the  disease  on 
a  steamship,  among  persons  who  drank  the  milk  of  a  herd  of 
goats  that  were  being  brought  to  America.^  The  goats  were 
not  sick.  Horrocks^  shows  that  probably  one  or  more 
animals  in  every  herd  are  excreting  the  germs  in  the  milk 
and  urine,  and  that  50  per  cent  give  evidence  by  serum 
reaction  that  they  are,  or  have  been,  infected.  Other  in- 
vestigations show  that  as  high  as  10  per  cent  of  milch 
goats  have  the  germs  in  their  milk,  although  they  present 
no  symptoms  of  the  disease.  Carriers  are  also  common 
among  human  beings.  Shaw^  found  that  10  of  525  well 
persons  were  excreting  the  germs  in  the  urine.  Ross,^ 
of  Port  Said,  found  the  bacillus  not  constant  in  cither  milk 
or  l)lood. 

Meningococcus  in  Nose.  —  While  the  germ  of  epidemic 
cerebro-spinal  meningitis  (Micrococcus  meningitidis)  has  been 

1  Hewlett,  Practitionor  (Lond),  1008,  LXXX,  222. 

2  Bruce,  Nature,  LoiuL,  190.S,  LXXVIII,  39. 

»  U.  S.  Pub.  Health  and  Mar.  Hosp.  Scrv.  Hyg.  Lab.  Bull.  No.  41, 
203. 

*  ITorrocks,  Rep.  of  Commission  of  Roy.  Soc,  1905-G,  Pts.  Ill,  IV. 
6  Shaw,  .1.  Roy.  Army  Med.  (brps,  Lond.,  1900,  VI,  638. 
'  Ross,  J.  Roy.  Army  Med.  Corps,  Lond.,  1911,  XI. 


CARRIERS  AND  MISSED  CASES  73 

known  for  many  years,  it  is  only  very  recently  that  any  ex- 
planation has  been  forthcoming  as  to  the  mode  of  infection. 
The  finding  of  the  organism  in  the  nose  of  patients  suggests 
the  possibility  that  infection  may  pass  to  the  brain  from  this 
point.  It  is  theoretically  possible  for  infection  to  take  place 
through  the  cribriform  plate  of  the  ethmoid  bone,  or,  as  sug- 
gested by  Westenhoeffer,^  by  the  lymphatics  from  the  pha- 
ryngeal tonsils,  or  as  some  think,  by  absorption  from  the 
alimentar}^  canal  and  passage  through  the  lymph  channels  or 
the  general  circulation.  The  organism  is  certainly  found  in 
the  blood  in  a  considerable  number  of  cases."  What  the  exact 
route  to  the  brain  is,  however,  has  not  yet  been  determined. 

That  the  germ  of  this  disease  is  found  in  the  nose  of  the 
sick  is  now  generally  recognized,  though  considerable  doubt 
has  been  thrown  on  the  accuracy  of  some  of  the  earlier  obser- 
vations, as  this  organism  is  not  readily  distinguished  from 
the  cocci  frequently  found  in  the  normal  nose.  Culture  and 
agglutination  tests  are  now  recognized  as  the  only  valid 
methods  of  differentiation.  Among  those  who  have  certainly 
isolated  it  in  a  considerable  number  of  instances  from  the 
nasal  mucous  membrane  of  cerebro-spinal  meningitis  cases 
may  be  mentioned  Dunham,^  Weichselbaum  and  Gohn,*  Lin- 
gelsheim,''  Goodwin  and  von  ShoUy  ^  and  others. 

Causes  Rhinitis. — That  this  micrococcus  is  frequently  found 
in  the  nose  of  contacts,  and  other  persons  showing  no  symp- 
toms of  the  disease,  is  now  well  established.  An  interesting 
case  is  that  of  Kiefer,^  who  while  working  with  a  culture  in 
the  laboratory  developed  a  severe  rhinitis  and  succeeded  in 

1  Westenhoeffer,  Berl.  klin.  Wchnschr.,  1905,  XLII,  737. 
^  Bimie  and  Smith,  Am.  J.  M.  Sc,  Phila.,  1907,  CXXXIV,  582,  and 
Simon,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  1938. 

3  Dunham,  J.  Infect.  Dis.,  Chicago,  1906  [Suppl.  No.  2],  10. 

*  Weichselbaum  and  Gohn,  Wien.  kUn.  Wchnschr.,  1905,  XVIII,  625. 

*  Lingelsheim,  Klin.  Jahrb.,  Jena,  1906,  XV,  373. 

*  Goodwin  and  von  Sholly,  J.  Infect.  Dis.,  Chicago,  1906  [Suppl. 
No.  2],  21. 

'  Kiefer,  Berl.  klin.  Wchnschr.,  1906,  XXXIII,  628. 


74  THE  SOURCES  AND  MODES  OF  INFECTION 

recovering  the  micrococcus  from  his  nose.  A  similar  case  was 
reported  to  me  by  P.  E.  Rauschenbach,  at  the  time  working 
in  a  hospital  at  Newark.  Ford^  also  had  a  case  of  this  kind. 
Meningococcus  in  Contacts.  —  Among  those  who  have 
found  the  organism  in  well  persons  may  be  mentioned  Weich- 
selbaum  and  Gohn,^  who  obtained  it  in  3  of  24  persons  exam- 
ined. Ostermann^  found  it  in  17  of  24  contacts  in  Breslau, 
but  his  methods  of  employing  the  agglutination  test  have 
been  called  in  question.  One  well  child  in  whose  nose  the 
germs  were  found  was  taken  sick  three  days  later  and  died 
the  next  day.  Many  of  the  carriers  had  pharyngitis  and 
rhinitis.  Of  49  children  in  schools  where  these  carriers  at- 
tended, 2  showed  the  meningococcus,  and  one  of  these  had 
been  playing  with  a  carrier.  Ostermann  failed  to  find  it  in 
50  persons  who  had  not  come  in  contact  with  cerebro-spinal 
cases.  Goodwin  and  von  ShoUy,  in  New  York,  obtained  it 
in  5  of  45  contacts,  and  a  similar  coccus  which  did  not  agglu- 
tinate, in  2  of  55  medical  students  not  contacts.  Bolduan^ 
found  the  organism  in  10  per  cent  of  150  contacts.  Lingels- 
heim,'^  during  an  extensive  outbreak  in  Beulen,  Prussia,  found 
the  organism  in  the  nose  of  26,  or  9  per  cent  of  289  contacts. 
Later  he  found  it  in  4  of  56  school  children, but  all  4  came  from 
families  where  there  had  been  cases  of  the  disease.  In  2  of 
the  4  cases  no  agglutination  test  Avas  applied.  In  the  cases 
of  the  disease  examined  by  Lingelsheim  the  micrococcus  dis- 
appeared by  the  fifth  day  in  66  per  cent,  and  by  the  sixth  to 
tenth  day  in  24  per  cent.  In  4.39  per  cent  of  the  cases  it  per- 
sisted over  three  weeks,  and  in  1  case  it  was  found  three 
months  from  the  beginning  of  the  attack. 

1  Quoted  by  Councilman,  J.  Am.  M.  Aas.,  1905,  XLIV,  999. 

2  Weichselbaum  and  Gohn,  Wion.  klin.  Wchnschr.,  1905,  XVIII, 
625. 

'  Ostermann,  Deutsche  mod.  Wohnschr.,  1906,  XXXII,  414. 
*  Bolduan,  Med.  Times,  N.  Y.,  1908,  XXXVI,  193. 
'  LinKclsheim,  Deut.selie  med.  Wchnschr.,  1905,  XXXI,  1017,  1217; 
Klin.  Jahrl).,  Jena,  1908,  XIX,  519. 


CARRIERS  AND  MISSED  CASES 


75 


Infection  in  the  Family. —  Bruns  and  Hohn^  found  that  the 
proportion  of  carriers  decreased  as  the  outbreak  decreased. 
This  is  shown  in  the  following  table: 


March , 
April.  . 
May. . 
June . . 
July.. 
August 


Reported 
Cases. 

No.  of 
Families 

No.  of  Well 

Persons 
Examined. 

No.,  of 
Carriers. 

148 

7 

23 

14 

278 

39 

135 

67 

327 

42 

172 

81 

188 

23 

93 

34 

146 

21 

67 

18 

68 

22 

119 

10 

Per  cent  of 
Carriers. 


61 
50 
47 
36 
27 
8.5 


They  found  that  of  the  fathers  in  these  families  60  of  113 
carried  the  germs;  of  the  mothers,  39  of  114;  of  children  in  the 
families,  118  of  .360;  and  of  other  members  of  the  families 
7  of  22  were  carriers. 

Persistence  of  Infection.  —  Bruns  and  Hohn  give  for  the 
duration  of  the  infection  the  following: 


For  8  days 28  cases 

2  weeks 18  cases 

3  weeks 13  cases 

4  weeks 10  cases 


For  0  weeks 4  cases 

6  weeks 3  cases 

7  weeks 3  cases 

8  weeks 1  case 


Selter,  in  Bonn,-  has  observed  a  very  much  longer  persist- 
ence of  the  infection.  In  the  case  of  a  mother  and  daughter 
who  recovered  from  the  disease,  the  cocci  persisted  from 
February  3  to  June  4.  The  father  in  this  family,  who 
had  not  been  sick,  yielded  positive  findings  in  May,  June, 
July  and  August,  and  had  in  all  probability  been  infective 
for  seven  months.  In  another  family  where  the  disease  ap- 
peared, the  6  well  persons  were  carriers  at  one  time  or 
another  from  February  18  to  June  5,  during  which  period 

1  Bruns  and  Hohn,  Klin.  Jahrb.,  Jena,  1907-08,  XVIII,  285. 
'  Selter,  Klin.  Jahrb.,  Jena,  1908-09,  XX,  457. 


76  THE  SOURCES  AND  MODES  OF  INFECTION 

they  were  examined  twelve  times.  Sometimes  the  examina- 
tions were  positive  and  sometimes  negative,  which  is  just 
what  occurs  in  the  examination  of  typhoid  and  diphtheria 
carriers.  This  apparent  intermittency  may  be  due  in  part 
to  faulty  technique,  and  in  part  to  the  temporary  absence 
of  the  bacteria.  In  the  69  examinations  of  the  family 
above  referred  to,  49  were  positive  and  20  negative.  Selter 
could  find  no  difference  between  the  cocci  found  in  the 
sick  and  in  the  carriers,  but  he  was  not  able  to  trace  a 
case  of  sickness  to  any  of  his  known  carriers.  Kirchner,^ 
in  Hamburg,  found  22,  or  9.7  per  cent,  carriers,  out  of  237  well 
members  of  infected  families,  but  in  3  families  all  the  mem- 
bers were  carriers,  and  in  10  other  families  75  per  cent  were. 
Most  of  these  were  adults.  In  two  instances  the  infection 
persisted  44  and  66  days  respectively.  Vagedes  ^  reports  3 
cases  in  barracks  at  Charlottenburg.  Of  58  hospital  attend- 
ants, etc.,  there,  4  were  carriers,  and  of  593  of  the  soldiers  10 
only  were  carriers.  On  a  second  examination  five  days  later 
1  only  was  found,  and  nineteen  days  later  none.  By  the  iso- 
lation of  carriers  the  disease  was  "  stamped  out,"  but  it  will 
be  noticed  that  the  infection  was  not  widely  diffused  before  it 
was  recognized.  Bochalli,^  in  certain  barracks  where  the 
disease  prevailed,  found  10  of  16  roommates  of  the  sick,  or 
62  per  cent,  to  be  carriers.  Of  485  in  other  companies,  42,  or 
8.6  per  cent,  were  infected.  Usually  the  germs  quickly  dis- 
appeared, but  in  one  case  they  persisted  for  four  and  a  half 
months.  In  another  instance  a  nurse,  going  to  a  district 
where  there  was  no  meningitis,  was  attacked  about  one  month 
later.  Similar  observations  have  been  made  in  several  places 
during  the  recent  outbreak  in  Scotland.  Buchanan,*  in  Glas- 
gow, found  the  micrococcus  in  81,  or  26.3  per  cent  of  308  con- 

»  Kirchner,  Klin.  Jahrb.,  Jena,  1908,  XIX,  473. 
'  VuKodos,  Deutsche  mil.-iirztl.  Ztschr.,  Borl.,  1907,  XXIII,  647. 
•'  Bochalli,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Lcipz.,  1908,  LXI, 
454. 

*  Buchanan,  San.  Rcc,  Lond.,  1907  n.  a.,  XI,  245. 


CARRIERS  AND  MISSED  CASES  77 

tacts  in  74  families.  Most  of  them  were  over  fifteen  years  of 
age.  In  14  families  he  obtained  it  from  more  than  one 
person,  in  2  instances  from  five.  In  4  instances  it  was 
found  in  the  nose  two  years,  one  year,  one  year,  and  three 
months,  respectively,  after  an  attack.  He  quotes  Arbuckle, 
medical  officer 'of  health  of  Partick,  as  finding  23.1  per  cent 
of  230  contacts  infected.  In  Leith,  Fraser  and  Comrie  ^ 
found  it  in  10,  or  14  per  cent,  of  69  contacts.  Of  these  5  were 
adults  whose  children  were  sick,  and  all  of  whom  had  worked 
on  a  ship  in  the  air  of  whose  engine  room  meningococci  were 
found.  Bethge,^  immediately  after  the  appearance  of  the 
first  case  in  a  certain  institution,  found  that  of  187  persons 
66  were  carriers. 

Found  only  in  Those  near  Sick.  —  The  micrococcus  which 
is  the  cause  of  this  disease,  while  frequently  noted  in  contacts, 
is  rarely  found  in  those  not  exposed  to  the  disease.  Oster- 
mann,  when  there  were  no  cases  about,  failed  to  find  the  germ 
in  50  children  and  in  many  adults.  Bolduan  did  not  find  it 
in  150.  Kolle  and  Wassermann^  recovered  the  germs  from 
2  of  114  persons,  but  one  had  been  in  contact  with  the  disease, 
and  the  other  shortly  became  sick.  Bochalli  found  none  in 
40  men  in  a  non-infected  regiment,  Lingelsheim*  none  in 
129  persons  otherwise  sick,  and  none  in  184  non-exposed  chil- 
dren, and  he  cites  Droba  and  Kucera  as  finding  none  among 
210  children  living  where  there  was  no  meningitis.  In  23  per- 
sons not  exposed  to  the  disease  and  examined  by  Fraser  and 
Comrie  none  of  these  organisms  were  found.  Arkwright* 
failed  to  find  them  in  54  well  persons,  and  Flexner"  could 
find  none  in  50  persons  in  Philadelphia  at  a  time  when  the 
disease  was  not  present  in  the  city. 

'  Fraser  and  Comrie,  Scot.  M.  &  S.  J.,  Edinb.,  1907,  XXI,  18. 

2  Bethge,  Deutsche  med.  Wchnschr.,  1910,  XXXV,  66. 

'  Kolle  and  Wassermann,  Klin.  Jahrb.,  Jena.,  1906,  XV,  507. 

*  Lingelsheim,  Klin.  Jahrb.,  Jena,  1906,  XV,  373. 
6  Arkwright,  J.  Hyg.,  Cambridge,  1907,  VII,  145. 

•  Flexner,  J.  Exper.  M.,  N.  Y.,  1907,  IX,  105. 


78  THE  SOURCES  AND   MODES  OF  INFECTION 

As  Lingelsheim  says,  it  appears  that  the  nearer  we  approach 
cases  of  the  disease  the  more  numerous  carriers  are,  and  the 
more  extensive  the  outbreak  the  more  numerous  they  are. 
Adults  are  more  commonly  infected  than  children.  Fliigge 
thinks  that  carriers  are  ten  to  twenty  times  as  numerous  as 
cases,  and  that  is  doubtless  true. 

Infection  by  Carriers.  That  carriers  are  the  chief  source 
of  the  disease  is  the  opinion  of  those  Germans  who  have  lately 
had  experience  in  severe  outbreaks,  and  it  is  shared  by  the 
Scotch  health  officers.  Lingelsheim  says  that  there  is  no 
bacteriological  or  epidemiological  evidence  to  show  that  the 
sick  are  more  dangerous  than  the  well,  otherwise  the  cases 
would  occur  in  groups.  On  the  contrary  the  carriers  mingling 
freely  with  the  public  are  the  most  dangerous.  Jehle  ^  states 
that  23  cases  occurred  in  children  in  the  families  of  miners. 
None  of  the  miners  were  sick,  but  when  they  were  transferred 
to  another  mine,  children  there  soon  began  to  develop  the 
disease.  Their  parents  were  doubtless  carriers.  Meyer  ^ 
reports  an  instance  where  carriers  gave  rise  to  three  cases. 
At  Leith,  Buchanan^  says  that  the  first  few  cases  could  be 
traced  to  carriers,  and  Thomson*  makes  a  similar  statement 
regarding  the  early  cases  in  Lanarkshire.  Flatten ''  gives  the 
details  of  numerous  instances  of  the  transmission  of  the  dis- 
ease by  well  persons. 

Carriers  explain  Spread  of  Disease.  —  Previous  to  the  dis- 
covery of  the  presence  of  the  spcnnfic  organism  of  cerebro- 
spinal meningitis  in  the  nose,  and  particularly  in  the  nose  of 
contacts,  the  mode  of  extension  of  the  disease  was  a  mystery. 
Though  certainly  an  infectious  disease,  and  appearing  in  epi- 
demics, often  quite  severe,  it  was  apparently  only  slightly  if 

•  Jehle,  cited  by  Warrington,  J.  Roy.  San.  Inst.,  Lend.,  1907,  XV,  656. 
'  Meyer,  Centralhl.   f.   Haktcriol.  [etc.],  I  Abt.   Orig.,  Jena,   1909, 

XLIX,  305. 

3  liuclianan,  Brit.  M.  J.,  Loml.,  1907,  II,  852. 

*  Thomson,  Mod.  PrcHS  &  VArc,  Lond.,  1908,  n.  b.,  LXXXVI,  344. 
"  Flatten,  Khn.  Juhrb.,  Jona,  1906,  XV,  265. 


CARRIERS  AND   MISSED  CASES 


79 


at  all  contagious.  Personally,  out  of  over  a  hundred  cases,  I 
have  only  twice  seen  two  cases  in  the  same  family,  and  have, 
except  in  those  instances,  never  been  able  to  trace  connection 
between  any  two  cases.  Cases  are  frequently  treated  in  con- 
siderable numbers  in  general  hospitals  all  over  the  world,  and 
infection  of  others  has  rarely,  if  ever,  taken  place.  In  New 
York  a  greater  degree  of  contagiousness  has  been  noted  than 
in  most  places.^  Of  1500  consecutive  cases,  112,  or  7  per  cent, 
were  secondary  cases  in  the  family.  It  is  said  that  when  more 
than  one  case  occurs  in  a  family  they  all  are  usually  taken  sick 
at  about  the  same  time,"  but  this  was  not  so  in  New  York. 
The  following  shows  the  date  at  which  the  secondary  cases 
appeared  in  that  city: 


Where  First  Cases  were  removed  to 
Hospital . 

Where  First  Case  remained  at  Home 

No.  of  Secondary 
Cases. 

Interval. 

No.  of  Secondary 
Cases. 

Interval. 

14 
5 

1-7  days 
1-2  weeks 

3 
4 

1  day 

2  days 

4 

2-3      " 

1 

3     " 

3 

3-4      " 

1 

5     " 

2 

4-5      " 

1 

6     " 

3 

5-6      " 

4 

7     " 

2 

7-8      " 

1 

9     " 

1 

3  mos. 

1 

11     " 

34 

1 

1 

18 

21     " 
30     " 

The  34  cases  which  developed  after  the  removal  of 
the  primary  case  to  the  hospital  indicate  either  that  the 
germ  of  the  disease  remained  in  the  house,  on  fomites,  which 
is  highly  improbable,  as  its  powers  of  resistance  are  extremely 


1  Am.  Pub.  Health  Ass.  Rep.,  1905,  XXXI,  359. 

»  Bolduan  and  Goodwin,  Med.  News,  N.  Y.,  1905,  LXXXVII,  1222. 


80 


THE  SOURCES  AND  MODES  OF  INFECTION 


slight,  or  that  unrecognized  carriers,  persons  with  the  coccus 
growing  in  the  nose,  remained  behind,  a  supposition  which 
is  entirely  in  accord  with  bacteriological  findings.  In  Glas- 
gow,i  of  194  cases,  7,  or  4.1  per  cent,  were  secondary  cases  in 
the  family.  Some  of  these  occurred  after  disinfection.  It  is 
not  unlikely  that  the  more  extensive  the  outbreak  the  more 
numerous  will  be  the  "  secondary  "  cases  in  the  family.  In 
Oppeln,  where  there  was  a  very  severe  outbreak,  Flatten  ^ 
found  the  number  of  secondary  cases  as  follows  in  successive 
months  of  the  outbreak: 


No.  of  Families. 

No.  of  Cases. 

January 

February 

March 

71 
143 
257 
310 
349 
374 

79 
163 
296 
368 
414 
439 

April 

May 

June 

If,  as  appears,  the  meningococcus  is  frequently  found  in 
the  nose  of  sick  persons  and  of  contacts,  the  mode  of  exten- 
sion of  the  disease  becomes  apparent.  Observations  indicate 
that  a  very  considerable  number  of  persons  who  come  in  con- 
tact with  cases  of  this  disease  carry  the  organism  on  their 
mucous  membrane.  Yet  very  few  of  these  persons  ever  be- 
come sick.  It  appears  that  the  development  of  the  cerebro- 
spinal symptoms,  that  is  the  disease  as  we  know  it,  is  really 
a  rather  unusual  accident  of  a  not  uncommon  harmless  infec- 
tion of  the  nasal  passage.  We  can  therefore  understand  how 
the  disease,  though  apparently  showing  little  contagiousness, 
is  nevertheless  a  strictly  contagious  disease.  It  extends  almost 
entirely  through  the  agency  of  carriers.  Sometimes,  as  was 
previously  stated,  these  carriers  can  be  discovered,  particu- 

^  Rep.  Med.  Off.  Health,  Glassow,  1906,  89. 
'  Flatten,  Klin.  Jahrb.,  Jeua,  1906,  XV,  228. 


CARRIERS  AND  MISSED  CASES  81 

larly  early  in  an  outbreak.  The  appearance  of  cases  in  dif- 
ferent localities  in  a  community,  and  at  varying  intervals,  is 
readily  explained  by,  and  is  almost  a  proof  of,  the  existence 
of  a  considerable  number  of  undiscovered  carriers. 

Meningitis  an  Accident  of  Infection. — The  growth  of  the 
germs  in  the  nose  cannot  properly  be  considered  the  "incu- 
bation" of  the  disease.  Inoculation  experiments^  indicate 
that  the  nervous  symptoms  develop  in  a  very  few  hours  after 
the  specific  bacteria  are  injected  into  the  meninges.  There 
is  much  evidence,  as  given  above,  to  show  that  the  germs  may 
grow  on  the  surface  of  the  nasal  mucous  membrane  for  days, 
weeks  and  perhaps  months,  but  when  they  once  gain  access 
to  the  meninges  the  symptoms  of  the  disease  speedily 
develop. 

Meningitis  also  occurs  as  a  result  of  infection  by  the  pneu- 
mococcus.  The  disease  thus  caused  is  not  essentially  different 
from  the  epidemic  form.  The  number  of  well  carriers  of  the 
pneumococcus  is  enormously  greater,  and  is  much  more  con- 
stant than  is  the  number  of  carriers  of  the  meningococcus, 
and  the  chance  of  the  former  invading  the  meninges  and  caus- 
ing sickness  is  small,  very  much  less  than  the  chance  of  the 
latter  doing  so.  In  either  case  it  may  be  considered  an  unfor- 
tunate accident  of  a  usually  benign  infection. 

Inutility  of  Isolation  of  Meningitis.  —  If  these  views  are 
correct,  little  can  be  done  by  means  of  isolation  to  prevent 
the  spread  of  the  disease.  When  an  outbreak  occurs,  there 
is  certain  to  be  a  large  number  of  carriers  that  cannot  be 
found  or  isolated.  To  isolate  the  sick,  and  even  those  in 
immediate  contact  with  the  sick,  will  probably  never  make 
any  appreciable  difference  in  the  progress  of  the  disease,  that 
is  if  the  findings  of  to-day  are  confirmed  by  more  extended 
observations.  By  the  time  several  cases  have  developed  in 
a  community,  there  will  probably  usually  be  a  considerable 
number  of  carriers  who  cannot  be  found.     Stringent  isola- 

1  Lingelsheim,  Deutsche  med.  Wchnschr.,  1905,  XXXI,  1017,  1217; 
Flexner,  J.  Exper.  M.,  N.  Y.,  1907,  IX,  142. 


82  THE  SOURCES  AND   MODES  OF  INFECTION 

tion  of  the  families  of  known  cases  will  accomplish  little,  and 
will  work  much  hardship  and  injustice. 

Diphtheria  Bacilli  in  Well  Persons.  —  Loeffler  ^  himself  in 
1884  found  diphtheria  bacilli  in  a  person  who  was  not  sick, 
and  in  1889  Roux  and  Yersin^  called  attention  to  the  per- 
sistence of  diphtheria  bacilli  on  the  mucous  membranes  of 
convalescents,  and  their  observations  were  at  intervals  sub- 
stantiated by  others.  In  1894  Park  and  Beebe  ^  examined  the 
throats  of  330  healthy  persons  who  had  not,  so  far  as  known, 
been  in  contact  with  diphtheria  cases,  and  found  diphtheria 
bacilli  in  24,  or  7.3  per  cent,  but  of  these  only  8,  or  2.4  per  cent, 
of  the  330  were  virulent.  These  authors  minimized  the  dan- 
ger to  be  apprehended  from  these  carriers,  and  although  for 
some  time  similar  observations  were  reported,  they  were  gen- 
erally, and  are  even  now  by  many,  considered  of  little  impor- 
tance. It  seems  to  me  otherwise,  and  therefore  a  considerable 
number  of  these  observations  are  here  summarized.  Miiller  * 
examined  in  routine  92  children  sick  with  diseases  other  than 
diphtheria,  in  Heubner's  clinic,  and  reported  that  12,  or  13 
per  cent,  were  infected  with  diphtheria,  but  only  6  of  the  12 
were  tested  on  guinea  pigs.  Later  18  children  in  the  same 
institution,  who  had  negative  cultures  on  admission,  were 
found  to  harl)or  the  ])acilli.  Kober ''  in  Brcslau  found  that 
of  600  school  children  2.5  per  cent  were  carriers  of  diphtheria 
bacilli,  but  in  only  0.83  per  cent  of  the  GOO  were  they  virulent. 
At  Baltimore,"  in  1899,  during  an  exceptional  prevalence  of 
diphtheria  in  a  number  of  schools,  culturc^s  were  taken  from 
4068  pupils  apparently  well,  and  of  these  157,  or  3.8  per  cent, 

*  Loefflcr,  The  Bacteriology  of  l^ii)litlieria,  Nuttall  and  Graham- 
Smith,  Cambridge,  1908,  31. 

»  Roux  and  Yorsin,  Ann.  de  I'Inst.  Pasteur,  1890,  IV,  385. 

^  Park  and  Beebe,  Med.  Rec,  N.  Y.,  1894,  XLVI,  385;  Sci.  Bull.  1, 
Dept.  Health  N.  Y.  City,  1895. 

^  Miiller,  Jahrb.  f.  Kinderh.,  189G,  XLIII,  54. 

'  Kober,  Ztschr.  f.  Hyg.  u.  Infeetionskrankh.,  Leipz.,  1899,  XXXI, 
433. 

•  Baltimore,  Rep.  Com.  of  Health,  1899,  9G;  1900,  85. 


CARRIERS  AND  MISSED  CASES  83 

showed  diphtheria  bacilli.    The  next  year,  of  351  examined, 
23,  or  6.6  per  cent,  were  positive. 

Varieties  of  Bacilli  found.  —  Reports  of  the  finding  of  diph- 
theria bacilli  in  well  persons  would  have  more  value  if  it  were 
made  clear  what  was  meant  by  the  term  diphtheria  bacilli. 
The  bacillus  varies  greatly  in  form,  and  those  who  have 
studied  it  most  carefully  are  by  no  means  agreed  as  to  what 
should  or  should  not  be  properly  so  called.  Fortunately 
Wesbrook's  classification  of  all  these  varieties,  both  admitted 
and  questioned,  renders  it  possible  to  interpret  properly  the 
reports  of  all  who  will  take  the  trouble  to  use  his  nomencla- 
ture, and  it  is  to  be  regretted  that  more  do  not  use  it.  Again, 
diphtheria  bacilli  are  quite  as  frequently  found  in  the  nose  as 
in  the  throat,  but  few  observers  state  whether  the  cultures 
were  taken  from  throat  or  nose  or  both.  For  the  purpose  of 
securing  definite  data  from  a  large  number  of  cases,  a  col- 
lective investigation  was  undertaken  by  the  Massachusetts 
Association  of  Boards  of  Health.^  The  number  of  persons 
examined  was  4250  in  different  parts  of  the  United  States. 
Most  of  them  had  probably  not  been  directly  exposed  to  diph- 
theria except  in  Minnesota,  where  most  of  the  cultures  were 
taken  from  schools  and  institutions  where  there  had  recently 
been  cases  of  the  disease.  The  majority  of  the  persons  ex- 
amined were  adults,  and  cultures  were  taken  from  both  throat 
and  nose.  Of  all  persons  examined,  2.89  per  cent  had  "granu- 
lar "  forms  of  diphtheria  bacilli,  i.e.,  those  showing  polar 
staining  with  methylene  blue.  If  "  barred  "  and  other  aber- 
rant types  are  to  be  considered  as  diphtheria  bacilli,  as  they 
are  by  some,  the  number  of  cultures  to  be  reported  positive 
would  have  been  more  than  doubled.  Referring  only  to  the 
typical  granular  types,  1.46  per  cent  of  all  persons  showed 
throat  infection  (either  with  or  without  concurrent  nose  infec- 
tion) and  2.07  per  cent  showed  nose  infection  (either  with  or 
without  concurrent  throat  infection).  In  the  different  cities 
the  percentage  of  infected  persons  varied  from  0.43  in  Provi- 

1  J.  Mass.  Ass.  Bds.  Health,  Bost.,  1902,  XII,  74. 


84  THE  SOURCES  AND   MODES  OF  INFECTION 

dence,  where  particular  care  was  taken  to  avoid  contacts, 
most  of  the  cultures  being  taken  from  schools  where  there 
had  been  no  diphtheria  for  at  least  two  years,  to  3.66  in  the 
Willard  State  Hospital,  and  6.03  in  Minnesota,  in  both  of 
which  localities  there  had  recently  been  diphtheria  in  the 
institutions  examined.  There  were  47  tests  for  virulence,  of 
which  8,  or  17  per  cent,  were  positive.  Recently  cultures  were 
taken  from  school  children  in  Brighton  (Boston)  by  Slack.' 
Of  over  4000  children  examined  by  throat  and  nose  culture  on 
two  occasions,  1.93  per  cent  showed  diphtheria  bacilli.  Of 
these  8  were  tested  for  virulence,  of  which  all  proved  to  be  non- 
virulent.  Most  of  these  children  were  excluded  from  school 
until  free  from  bacilli,  but  all  of  them  had,  of  course,  been 
carrying  bacilli  in  school  for  a  longer  or  shorter  period.  No 
case  of  clinical  diphtheria  was  traced  to  any  of  these  carriers, 
either  in  school  or  out  of  school.  These  facts  have  been  ad- 
vanced as  evidence  that  the  danger  from  such  carriers  is  a 
negligible  factor  in  contrast  with  the  danger  from  conva- 
lescents whose  bacilli  are  usually  virulent.  But  in  Providence 
in  1908,  73  convalescents  carrying  diphtheria  bacilli  were 
admitted  to  school,  and  it  is  not  known  that  they  were  in  any 
instance  the  source  of  new  cases  in  the  school,  and  in  all  but 
two  or  three  instances  it  is  certain  that  they  were  not. 
Forbes  '  cites  Meikle  as  reporting  27  carriers  discharged  from 
the  hospital  without  any  return  case.  These  facts  merely  in- 
dicate that  the  amount  of  danger  from  a  single  focus  of 
infection  is  much  less  than  is  generally  believed. 

Value  of  Bacteriological  Findings.  —  Neumann'  could  not 
find  any  diphtheria  bacilli  in  111  perfectly  normal  throats 
and  noses,  but  did  find  them  in  8  of  95  cases  suffering  from 
catarrhal  inflammation  of  the  mucous  surfaces.  He  does  not 
think  that  they  are  found  in  normal  throats,  but  certainly 
all  who  have  had  any  experience  in  taking  cultures  have  seen 

1  Slack,  Arms,  Wade  and  Blanchard,  J.  Am.  M.  Ass.,  1910,  LIV,  951. 

2  Forbes,  lirit.  M.  J.,  1909,  II,  522. 

'  Neumann,  Ztschr.f.Hyg.u.  Infectionskrankh.,  Leipz.,  1902,  XL,  33. 


CARRIERS  AND  MISSED  CASES  85 

numberless  cases  where  diphtheria  bacilli  were  found  in 
throats  which,  so  far  as  appearances  go,  were  perfectly  nor- 
mal. When  diphtheria  bacilli  are  found  on  a  reddened  or 
slightly  inflamed  mucous  surface,  the  abnormal  condition 
may  not  in  every  individual  case  be  due  to  their  presence,  for 
certainly  "  catarrhal  "  inflammations  of  nose  and  throat,  due 
to  other  causes  than  the  presence  of  diphtheria  bacilli,  are 
extremely  common.  The  evidence  is  that  at  present,  in  cities, 
from  1  to  2  per  cent  of  the  population  are  infected  with 
diphtheria  bacilli.  The  presence  of  diphtheria  bacilli  in  an 
inflamed  throat  may  be,  then,  in  1  or  2  per  cent  of  the  find- 
ings merely  a  coincidence.  It  is  safe  to  assume  that  in  all 
but  1  or  2  per  cent  the  presence  of  diphtheria  bacilli  stands 
in  causative  relation  to  the  inflammation  of  the  surface  on 
which  they  are  found. 

Diphtheria  Bacilli  in  Children.  —  In  Bristol,  Heaven^  ex- 
amined 704  children  (throat  and  nose)  connected  with  schools 
where  there  had  been  considerable  diphtheria,  and  found 
diphtheria  bacilli  in  24,  or  3.4  per  cent.  Of  758  cultures  taken 
from  schools  in  London  where  there  had  been  occasional  cases 
of  diphtheria,  58,  or  7.6  per  cent,  showed  the  bacilli."  Pen- 
nington^ examined  375  well  children  in  Philadelphia  schools, 
in  some  of  which  there  had  been  more  or  less  diphtheria,  and 
of  37  positive  cultures  from  these,  24  were  more  or  less  viru- 
lent. Of  125  pupils  from  four  other  schools  10.4  per  cent  gave 
positive  cultures,  about  half  of  which  were  virulent.  But 
Pennington  found  that  of  25  cultures  from  convalescents  22 
were  virulent.  In  the  city  of  Mexico,  of  300  school  children 
10,  or  3.3  per  cent,  showed  diphtheria  bacilh.*  Von  ShoUy  "^ 
examined  1000  tenement-house  children  in  New  York,  taking 
cultures  only  from  those  whose  throats  appeared  normal.  The 

1  Heaven,  Pub.  Health,  Lond.,  1902-03,  XV,  516. 

2  Rep.  Med.  Off.  Health,  Lond.,  1904,  Appendix  III,  25. 
^  Pennington,  J.  Infect.  Dis.,  Chicago,  1907,  IV,  36 

*  Fabela,  Rep.  Am.  Pub.  Health  Ass.,  1906,  XXXII,  Pt.  2,  199. 
'  Von  Sholly,  J.  Infect.  Dis.,  Chicago,  1907,  IV,  337. 


86  THE  SOURCES   AND   MODES  OF  INFECTION 

children  for  the  most  part  were  those  brought  to  hospitals 
and  dispensaries  for  treatment,  but  all  cases  were  excluded 
which  had  any  suggestion  of  sore  throat,  nasal  discharge, 
etc.  Of  these  1000  cases  5.6  per  cent  showed  diphtheria- 
like organisms,  of  which,  however,  only  1.8  per  cent  (of 
the  1000  cases)  proved  to  be  virulent.  In  50  of  the  cases 
nose  cultures  also  were  taken,  and  one  of  these  proved  to 
have  virulent  bacilli.  During  a  very  severe  outbreak  of  diph- 
theria in  Christiania,  Ustvedt'  examined  4277  school  children, 
and  found  diphtheria  bacilli  in  191,  or  4.5  per  cent.  Of  these, 
10  afterwards  developed  diphtheria.  Of  7  cultures  tested  for 
virulence  4  were  positive.  In  one  school  in  which  the  per- 
centage of  positive  cultures  was  9.2  during  the  outbreak,  it 
was  3.2  some  months  later.  In  a  school  in  the  country  where 
there  had  been  no  diphtheria  for  j'Cars,  no  bacilli  were  iso- 
lated from  86  pupils.  Ruediger^  found  diphtheria  bacilli  in 
3  of  51  normal  throats.  Gross ^  took  two  throat  and  nose 
cultures  from  314  children  (without  diphtheria)  on  admission 
to  the  Children's  Hospital  in  Boston,  and  isolated  diphtheria 
bacilli  from  26,  or  7.9  per  cent.  Five  were  tested  for  viru- 
lence, 4  of  which  were  positive.  Hewlett  and  Murray* 
found  that  58,  or  15  per  cent,  of  385  children  on  admission  to 
the  Victoria  Hospital  for  Children  in  London,  were  diphtheria 
carriers,  and  that  in  children  under  two  years  of  age  the  per- 
centage was  21.  Cobbett ''  at  Cambridge  reported  diphtheria 
bacilli  in  2.9  per  cent  of  650  well  persons,  many  of  whom  were 
contacts.    Some  had  mild  sore  throat. 

Diphtheria  Bacilli  in  Scarlet  Fever.  —  While  the  presence 
of  diphtheria  bacilli  in  scarlet  fever  cases  sheds  little  light 
on  their  prevalence  in  normal  throats,  it  is  of  much  interest 

'  Uatvedt,  Ztschr.  f.  Hyg.  u.  Infectionskninkh.,  Loipz.,  1906,  LIV, 
147. 

2  Ruediger,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVII,  1173. 

•  Hross,  Univ.  M.  Mag.,  Phila.,  1896-7,  IX,  4.5. 

*  Hewlett  and  Murray,  lirit.  M.  J.,  Lond.,  1901,  I,  1474. 
<>  Col)l)et(,  J.  Ilyg.,  ('aiiil)n(lgc,  1901,  I,  212. 


CARRIERS  AND  MISSED  CASES  87 

from  an  epidemiological  standpoint.  The  exudation  which 
frequently  covers  the  tonsils  in  scarlet  fever  is  often  mistaken 
clinically  for  a  sign  of  diphtheria,  and  such  cases  are,  before  the 
appearance  of  the  eruption,  often  reported  as  diphtheria,  so 
that  there  is  a  popular  impression  among  physicians  that  the 
two  diseases  are  frequently  combined,  and  that  the  presence 
of  scarlet  fever  predisposes  to  diphtheria.  While  bacteriolog- 
ical examinations  tend  to  show  that  diphtheria  infection  on 
scarlet  fever  is  not  so  common  as  is  often  assumed,  and  that 
many  cases  reported  as  a  combination  of  the  two  diseases  are 
not  really  such,  yet  diphtheria  bacilli  are  frequently  found  in 
cases  of  scarlet  fever,  more  frequently  than  they  are  found 
in  the  general  public  from  whom  the  scarlet  fever  cases  come. 
In  Providence  during  the  past  four  years  cultures  have 
been  taken  from  92  scarlet  fever  cases  in  their  homes,  of 
which  6,  or  6.5  per  cent,  were  positive.  Of  245  cultures  in  the 
hospital,  26,  or  10.6  per  cent,  were  positive.  During  the  pre- 
ceding three  years  116  cultures  were  taken,  but  it  was  not 
recorded  whether  they  were  from  hospital  or  home  cases,  and 
of  these,  5,  or  4.3  per  cent,  were  positive.  The  excessive  per- 
centage of  positive  findings  in  the  hospital  was  due  to  infec- 
tion after  admission.  Both  throat  and  nose  cultures  were 
taken  in  nearly  every  case.  In  the  Western  Fever  Hospital 
of  London,^  of  1019  throat  swabs  taken  from  the  same  num- 
ber of  scarlet  fever  patients  on  admission,  7.86  per  cent  were 
positive;  at  another  hospital  5.41  per  cent  of  203  cases,  and 
at  another  6.8  per  cent  of  87  cases.  Of  the  939  cases  at  the 
Western  Hospital  which  did  not  have  diphtheria  bacilli  on 
admission,  6  later  developed  diphtheria,  ranging  from  the  ninth 
to  the  fiftieth  day  after  admission,  and  28  more  acquired 
diphtheria  bacilli  without  being  sick.  Of  the  80  cases  that 
entered  infected,  4  developed  clinical  diphtheria  on  the 
fourth,  fifth,  seventh  and  thirty-first  days.  Soerensen^  found 
that  of  1 547  scarlet  fever  cases  examined  on  admission,  38,  or 

1  Cumpston,  J.  Hyg.,  Cambridge,  1907,  VII,  598. 

2  Soerensen,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  1898,  XXIX,  250. 


88  THE  SOURCES  AND  MODES  OF  INFECTION 

2.5  per  cent,  carried  diphtheria  bacilli.  During  a  service  of  two 
years  32  cases  of  diphtheria  occurred  in  the  scarlet  fever  wards 
among  about  1500  patients,  and  208  others  were  found  to  be 
infected  but  not  sick.  Ruediger^  found  diphtheria  in  4  of  75 
scarlet  fever  throats,  or  5.3  per  cent.  Garratt  and  Wash- 
bourn  ■  found  diphtheria  germs  in  8,  or  1.2  per  cent,  of  666 
scarlet  fever  cases.  In  Croydon,^  37,  or  17.3  per  cent,  of  213 
cases  of  scarlet  fever  were  shown  to  be  infected  with  diph- 
theria bacilli  on  admission  to  the  hospital.  In  Brighton,*  in 
1905,  33,  or  25.9  per  cent,  of  166  cases  of  scarlet  fever  had 
diphtheria  bacilli  present,  and  all  but  one  were  infected  on 
admission;  in  1907,  21  of  340  were  infected.  In  Bristol,^  of 
202  scarlet  fever  patients  in  the  hospital  in  1904,  75  per  cent 
had  positive  cultures  on  admission.  In  1905,  of  476  cases,  21 , 
or  4.4  per  cent,  were  positive,  besides  3  others  which  showed 
symptoms  of  the  disease.  In  Philadelphia,  of  700  scarlet 
fever  admissions,  11  per  cent  showed  diphtheria  bacilli. 

Percentage  of  Diphtheria  Carriers.  —  The  evidence  thus 
far  adduced  tends  to  show  that  diphtheria  bacilli  are  quite 
widely  distributed  in  the  urban  population  of  Europe  and 
America.  Perhaps  on  the  average  1  or  2  per  cent  harbor  the 
germs  of  this  disease  in  mouth  or  nose;  but  observations  also 
indicate  that  the  less  diphtheria  there  is  in  a  community, 
and  the  farther  removed  the  persons  examined  are  from  cases 
of  the  disease,  the  less  likely  they  are  to  be  infected.  Thus 
in  Christiania  during  an  outbreak,  9.2  per  cent  of  the  pupils 
in  a  certain  school  were  infected,  while  some  months  later 
the  ratio  was  only  3.2.  The  Massachusetts  Association  of 
Boards  of  Health  report  an  infection  of  6.03  per  cent  of  the 
school  children  recently  exposed  to  diphtlieria  in  Minneapolis, 
while  in  schools  in  Providence  where  there  had  been  no  diph- 

'  Ruediger,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVII,  1173. 
^  Garratt  and  Washbourn,  Brit.  M.  J.,  Lond.,  1899,  I,  893. 
'  Rep.  Med.  Off.  ITealth,  Croydon,  1004,  08. 
*  Rep.  Med.  Off.  Health,  Brighton,  1905,  42;  1907,  22. 
»  Rep.  Med.  Off.  llculth,  Briytol,  1904,  100;  1905,  71. 


I 


CARRIERS  AND  MISSED  CASES 


89 


theria  for  a  long  time  the  ratio  was  only  about  one-half  of 
1  per  cent. 

Percentage  among  Contacts.  —  There  are  numerous  obser- 
vations made  on  persons  brought  more  or  less  closely  in  con- 
tact with  the  sick,  which  show  that  under  such  conditions 

Percentage  of  Carriers  in  Diphtheria  Families,  Providence,  1897-1901. 


Ages. 

Persons  ex- 
amined. 

Number  of 
Carriers. 

Percentage 
of   Carriers. 

Under  1  year  .... 
1   "       

119 
112 

17 
15 

14.2 
13.3 

2  years 

3  "    

97 
112 

23 
25 

23.7 
22.3 

4     "    

116 

31 

26.7 

5     "    

120 

17 

14.1 

6     "    

137 

42 

30.6 

7     "    

130 

30 

23.1 

8     "    

119 

25 

21.0 

9     "    

113 

23 

20.3 

10     "    

139 

26 

18.7 

11     "    

79 

11 

13.9 

12     "    

127 

28 

22.0 

13     "    

86 

15 

17.4 

14     "     

88 

13 

14.7 

15     "    

70 

5 

7.1 

16     "    

64 

9 

14.0 

17     "    

57 

9 

15.7 

18     "    

57 

6 

10.5 

19     "    

45 

4 

8.8 

20     "    

34 

4 

11.7 

Adults 

2505 

277 

11.0 

Totals 

4526 

655 

14.4 

the  number  of  carriers  may  be  very  high.  For  several  years 
in  Providence  ^  cultures  were  taken  from  all  the  wage  earners 
in  the  family  at  the  time  the  case  was  reported,  and  from  all 
the  members  of  the  family  for  release,  that  is,  to  determine 


Rep.  Supt.  Health,  Providence,  1901,  44. 


90         THE  SOURCES  AND  MODES  OF  INFECTION 

the  end  of  isolation.  Only  throat  cultures  were  taken.  Of 
4526  such  contacts  examined  14.4  per  cent  were  found  to  be 
infected.  If  nose  as  well  as  throat  cultures  had  been  taken, 
and  if  cultures  had  been  taken  from  the  whole  family  about 
midway  in  the  course  of  the  disease,  I  imagine  the  percentage 
would  have  been  several  times  greater.  The  preceding  table 
shows  the  percentage  infected  at  different  ages.  The  women 
in  the  family  were  infected  very  much  oftener  than  the  men. 
It  was  noMced  that  in  about  10  per  cent  of  the  cases  some 
well  member  of  the  family  remained  infected  after  the  patient 
was  entirely  free  from  germs.  In  Glasgow,^  of  2305  contacts 
in  infected  families  9.2  per  cent  were  carriers. 

Percentage  of  Carriers  in  Infected  Schools.  —  In  a  certain 
school  in  Minnesota,"  of  263  well  children,  129,  or  49  per  cent, 
were  infected  with  the  granular  and  barred  types  of  the  bacil- 
lus. In  Bristol  ^  during  a  school  outbreak  in  1907,  of  190 
well  children,  12.5  per  cent  were  carriers.  At  the  Willard  Hos- 
pital for  the  Insane  during  an  outbreak,  of  1423  well  persons, 
189,  or  13  per  cent,  were  carriers.  At  the  State  Hospital  in 
California,  11.6  of  1115  persons  were  infected.^  In  Provi- 
dence during  an  outbreak  of  diphtheria  in  an  infant  asylum, 
of  175  children  and  adults,  116  or  66.2  per  cent,  proved  to  be 
infected  at  one  time  or  another,  but  this  was  only  after  many 
repeated  cultures  extending  over  a  period  of  some  months. 
Many  of  them  were  persistent  carriers,  one  of  them  remaining 
infected  for  twenty-two  months.  Crowley ''  in  a  school  out- 
break found  42  of  93  children  infected,  or  45  per  cent.  In 
Bermondsey,  London,''  the  children  in  diphtheria  families 
have  a  single  throat  culture  taken,  and  of  597  children  so 

1  Rep.  Med.  Off.  Health,  Glasgow,  1908,  71. 

2  Wcsbrook,  St.  Paul  M.  J.,  St.  Paul,  Minn.,  1900,  II,  219  [p.  6  of 
reprint]. 

'  Rep.  Med.  Off.  Health,  Bristol,  1907,  51. 

*  Rep.  (^alif.  St.  Bd.  He.alth,  190()-()S,  201. 

<•  Crowley,  J.  Roy.  San.  Inst.,  1904-05,  XXV,  807. 

•  Rep.  Med.  Off.  Health,  London,  1904,  31. 


CARRIERS   AXD   MISSED   CASES  91 

examined  64,  or  10.8  per  cent,  were  found  to  be  infected.  Of 
115  well  children  in  an  institution  in  Minneapolis,  Corbet  ^ 
found  29,  or  25.2  per  cent,  infected.  In  several  instances  the 
bacilli  presented  atypical  forms,  but  many  of  these  were  viru- 
lent. In  a  school  in  the  same  city,  where  there  had  been  some 
diphtheria,  he  found  that  20,  or  14.3  per  cent,  of  140  cultures 
showed  the  presence  of  typical  bacilli.^  Ustvedt,^  in  Chris- 
tiania,  found  17  per  cent  of  contacts  infected.  In  a  school  at 
Oakland,  California,^  25  per  cent  of  the  pupils  were  carriers. 
In  Glasgow,^  of  322  well  members  of  diphtheria  families  10.5 
per  cent  were  infected.  In  the  Duke  of  York's  school,  Lon- 
don, of  536  well  pupils  117,  or  20  per  cent,  showed  diphtheria 
bacilli,  and  of  these  10  later  had  diphtheria,  while  only  one 
of  the  "  free  "  boys  developed  it.  Of  13  cultures  from  the 
well  boys,  7  were  virulent,  though  mildly  so,  but  the  bacilli 
from  the  sick  also  showed  a  low  virulence.  It  is  worthy  of 
note  that  the  disease  recurred  in  this  school  for  two  or  three 
years.^  von  Sholly  ^  found  bacilli  in  20  of  202  contacts,  or 
about  10  per  cent,  and  of  these  14  were  virulent.  Buchanan* 
in  Glasgow  found  that  the  bacilli  were  virulent  in  66  per 
cent  of  21  healthy  carriers,  and  that  bacilli  recovered  from 
56  cases  of  the  disease  proved  virulent  only  in  74  per  cent. 
Aaser**  found  19  per  cent  of  contacts  in  cavalry  barracks  in- 
fected, and  20  per  cent  of  children  in  a  scarlet  fever  ward, 
Hellstrom  ^^  in  Stockholm,  of  786  soldiers  who  had  been  more 

'  Corbet,  Rep.  Com.  Health,  Minneapolis,  1905,  7. 

^  Rep.  Com.  Health,  Minneapolis,  1903,  16. 

'  Ustvedt,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,Leipz.,1906,  LIV,  147. 

<  Bull.  Calif.  St.  Bd.  Health,  November,  1906. 

6  Rep.  Med.  Off.  Health,  Glasgow,  1906,  135. 

^  Arkwright,  J.  Hyg.,  Cambridge,  1908,  VIII,  48  ;  Rep.  Med.  Off. 
Health,  Lond.,  1906,  36. 

'  von  Sholly,  J.  Infect.  Dis.,  Chicago,  1907,  IV,  337. 

*  Buchanan,  Brit.  M.  J.,  Lond.,  1909,  II,  519. 

«  Aaser,  Deutsche  med.  Wchnschr.,  1895,  XXI,  357. 

'"  Hellstrom,  cited  by  Kober,  Ztschr.  f.  Hyg.  u.  Infectionskrankh., 
Leipz.,  1899,  XXXI,  433,  and  by  Fibiger,  Bed.  klin.  Wchnschr.,  1897, 
XXXIV,  753. 


92  THE  SOURCES  AND  MODES  OF  INFECTION 

or  less  in  contact  with  diphtheria,  found  151,  or  19.2  per  cent, 
infected.  Goadby,^  in  586  pupils  in  a  school  where  there  had 
recently  been  21  diphtheria  cases,  found  that  190,  or  34.1 
per  cent,  were  carriers,  and  he  quotes  Meade  Bolton  as  finding 
45.5  per  cent  of  214  contacts  infected.  Of  the  children  ex- 
amined by  Goadby  262  had  enlarged  tonsils  and  196  abnor- 
mal throats.  In  another  school  where  there  had  been  no 
reported  cases,  18  of  100  were  infected. 

Berry  and  Washbourn"  report  17,  or  11.9  per  cent,  of 
infected  contacts  in  a  school  of  142  girls.  Lister  ^  found  48 
per  cent  of  125  contacts  in  Shadwell  Hospital  infected. 
Twentj^-four  of  them  had  nasal  discharge.  Park  and  Beebe* 
in  a  foundling  asylum  obtained  virulent  bacilli  and  one  non- 
virulent  form  from  5  of  55  contacts.  Fibiger,''  during  a  school 
outbreak  of  diphtheria,  recovered  the  bacilli  in  22,  or  16.4  per 
cent,  of  134  children.  Denny"  found  11  per  cent  of  200  chil- 
dren infected,  in  a  school  where  there  had  recently  been  4  cases 
of  diphtheria,  and  Graham-Smith,^  10.4  per  cent  of  519  school 
children.  Gabritschewsky*  in  the  Russian  military  service 
found,  during  the  prevalence  of  diphtheria,  that  20  per  cent 
of  the  well  persons  examined  were  carriers,  and  in  a  school 
in  Moscow,  at  a  time  when  there  was  much  diphtheria,  21  of 
66  well  children  showed  diphtheria  bacilli. 

Atypical  Diphtheria.  —  The  old  notion  was,  and  I  fear  that 
very  many  physicians  and  not  a  few  health  officers  so  believe 
to-day,  that  diphtheria  is  a  well  defined  disease  with  charac- 
teristic symptoms.    They  cannot  imagine  diphtheria  without 

'  Goadby,  Lancet,  Lond.,  1900,  I,  236. 
'  Berry  and  Washbourn,  Brit.  M.  J.,  Lend.,  1900,  I,  198. 
'  Lister,  Brit.  M.  J.,  Lond.,  1898,  II,  1338. 
*  Park  and  Beebc,  Med.  Rec,  N.  Y.,  1894,  XLVI,  385. 
'"  Fibiger,  Berl.  klin.  Wchnschr.,  1897,  XXXIV,  753. 
»  Denny,  Bost.  M.  &  S.  J.,  1900,  515. 
'  Graham-Smith,  J.  Hyg.,  Cambridge,  1903,  III,  216. 
"  Gabritschewsky,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1901, 
XXXVI,  45. 


CARRIERS  AND  MISSED  CASES  93 

serious  illness.  There  always  have  been,  however,  some  acute 
clinicians  who  thought  otherwise.  Jacobi  in  New  York  was 
among  the  foremost.  He  recognized  that  the  disease  often 
presented  a  mild  type  and  that  diagnosis  was  impossible. 
He  said  in  1884:  ^ 

"The  sj^mptoms  are  often  but  few.  A  little  muscular  pain 
and  difficult  deglutition  are,  perhaps,  all  that  is  complained 
of.  Women  will  quietly  bear  it;  men  will  go  about  their  busi- 
ness. .  .  .  There  is  as  much  diphtheria  out  of  bed  as  in  bed ; 
nearly  as  much  out  of  doors  as  indoors.  Many  a  mild  case 
is  walking  the  streets  for  weeks  without  caring  or  thinking 
that  some  of  his  victims  have  been  wept  over  before  he  was 
quite  well  himself.  .  .  .  Diphtheria  is  contagious.  Severe 
forms  may  beget  severe  or  mild  forms.  Mild  cases  may  beget 
mild  or  severe  cases." 

Under  Jacobi's  teaching  I  early  learned  to  look  for  such 
mild  cases,  and  I  remember  seeing  an  outbreak  in  a  children's 
home  during  the  early  eighties,  in  which  there  were  many 
very  mild  sore  throats  and  walking  cases.  Mild  diphtheria 
of  this  type  does  not  usually  come  to  the  notice  of  a  physician, 
and  when  it  does  is  frequently  not  recognized.  How  fre- 
quent such  cases  are  it  is  difficult  to  determine,  but  they  must 
be  very  numerous.  In  a  general  hospital  at  Chelsea^  (Lon- 
don), where  there  had  been  considerable  trouble  from  out- 
breaks of  diphtheria,  it  was  determined  to  take  cultures  from 
all  patients  admitted  who  showed  any  symptoms  of  sore 
throat.  Of  815  persons  so  examined  65,  or  7.3  per  cent,  gave 
positive  cultures.  In  New  York  City^  the  school  inspectors 
were  directed  to  take  cultures  from  all  children  showing  slight 
redness  of  the  throat  or  hypertrophied  tonsils.  Of  11,451 
cultures  757,  or  6.7  per  cent,  were  positive.  These  children 
were  not  in  any  sense  considered  as  ill,  yet  the  percentage 

1  Quoted  by  Solis-Cohen,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  32. 

2  Parkes,  Pub.  Health,  Lond.,  1902-03,  XV,  538. 

3  Letter  from  Dr.  Cronin,  N.  Y.  Bd.  Health,  Sept.  23,  1904. 


94  THE   SOURCES   AND   MODES  OF  INFECTION 

infected  is  certainly  much  higher  than  would  be  looked  for 
among  the  general  school  population.  In  Hartford  ^  during 
the  years  1900-1903  cultures  were  taken  from  2038  mild  .sore 
throats  seen  in  the  schools.  Of  these,  591,  or  29  per  cent,  were 
positive.  These  children  might  be  said  to  have  a  decided  sore 
throat,  though  they  were  all  well  enough  to  be  in  school. 
They  were  all  excluded  from  school.  During  the  same  period 
there  were  reported  in  Hartford  1537  cases  of  diphtheria,  so 
that  the  cases  found  in  the  manner  described  equaled  one- 
third  of  the  total  cases.  In  Indianapolis,^  at  a  time  when 
there  were  60  reported  cases  of  diphtheria  in  the  city,  a  dili- 
gent search  for,  and  taking  of  cultures  from,  sore  throats 
among  the  school  children  revealed  the  presence  of  46  other 
cases.  Everj^  one  knows  how  extremely  common  sore  throat 
and  tonsillitis  are,  and  even  if  only  a  very  small  proportion, 
much  less  than  29  per  cent,  of  these,  are  true  diphtheria,  the 
number  in  the  aggregate  must  be  very  large.  I  think  I  am  well 
within  bounds  when  I  assume  that  for  every  recognized  case  of 
diphtheria  there  is  at  least  one  sore  throat  which  is  also  diph- 
theria though  unrecognized.  Judging  from  the  proportion  of 
mild  cases  in  institution  outbreaks,  the  proportion  of  unrec- 
ognized, mild,  but  yet  clinical  cases,  must  be  much  greater 
than  that.  Careful  medical  inspection  often  discovers  that 
these  missed  cases  have  been  the  source  of  reported  cases. 
For  example,  the  Report  on  the  Health  of  the  City  of  Man- 
chester (England),  1906,  gives  a  list  of  29  cases  caused  in  this 
way  during  that  year. 

Rhinitis  and  Otitis.  —  Diphtheria  sometimes  assumes  a 
chronic  form  with  few  symptoms.  Indeed  some,  as  Neumann, 
believe  that  long  persistence  of  diphtheria  bacilli  in  throat 
and  nose  is  always  accompanied  by  local  disturbance.  That 
such  is  often  the  case  in  the  nose,  and  that  subacute 
chronic  rhinitis  may  be  a  form  of  diphtheria,  and  may  give 
rise  to    typical   pharyngeal    cases,   is    generally  recognized. 

'  Reps.  Bd.  Health,  Hartford,  1900  to  1903. 

^  Rep.  Dept.  Pub.  Health  &  Charities,  Iiuliaruipolis,  190S,  8. 


CARRIERS  AND  MISSED  CASES  95 

Park/  Abbott,^  Ravenel,^  Schaps/  Treitel  and  Koppel,^ 
DeStella,"  Ballin^  and  many  others  report  cases  of  chronic 
rhinitis  due  to  the  presence  of  the  diphtheria  bacillus.  The 
middle  ear  sometimes  suppurates  in  diphtheria,  as  it  does  in 
scarlet  fever,  though  less  frequently,  and  this  discharge  may 
remain  virulent  for  long  periods.^  I  happen  to  have  such  a 
case  under  observation  at  the  present  time. 

A  Real  Danger.  —  There  can  be  no  douljt,  then,  that  mild 
and  unrecognized  cases  of  diphtheria  are  very  common,  that 
convalescents  long  harbor  the  bacilli,  and  that  contacts  and 
other  carriers  are  very  numerous;  in  fine,  that  these  sources 
of  infection  far  outnumber  the  cases  of  recognized  sickness. 
But  are  these  really  sources  of  infection,  or  are  they,  as  so 
many  believe,  an  imaginary  danger  evolved  in  the  brain  of 
the  laboratory  worker  ?  It  is  well  again  to  emphasize  the 
fact  that  long  before  Klebs  and  Loeffler  identified  the  bacillus 
of  this  disease  a  few  able  clinical  observers  like  Jacobi  be- 
lieved that  evidence  pointed  clearly  to  the  great  danger  of 
these  unrecognized  sources  of  infection.  The  bacteriologists 
have  not  raised  the  bugaboo  of  carrier  infection,  they  have 
simply  explained  the  facts  which  observing  men  have  long 
recognized. 

Carriers  cause  Disease.  —  A  little  perusal  of  medical  liter- 
ature will  show  that  many  cases  are  reported  of  what  is 
apparently  the  distribution  of  diphtheria  by  carriers. 

Peck  ^  reports  an  instance  where  a  young  man  who  was 

1  Park,  Med.  Rec,  N.  Y.,  1892,  XLII,  121. 

2  Abbott,  Med.  News,  Phila.,  1893,  LXII,  505. 

3  Ravenel,  Med.  News,  Phila.,  1895,  LXVI,  537. 

*  Schaps,  Arch.  f.  Enderh.,  Stuttg.,  1905,  XL,  80. 

5  Treitel  and  Koppel,  Arch.  f.  Ivinderh.,  Stuttg.,  1895-96,  XIX,  107. 

6  DeStella,  Arch,  internat.  de  laryngol.  [etc.].  Par.,  1903,  XVI,  970. 
'  Ballin,  Jahrb.  f.  Kinderh.,  1903,  LVIII,  412. 

*  Newsholme,  Rep.  Med.  Off.  Health,  Brighton,  1906,  13;  Address  at 
Victoria  Univ.,  Manchester,  March  9,  1904,  21. 

»  Peck,  Brit  M.  J..  Lond.,  1895,  I,  971. 


96  THE  SOURCES  AND   MODES  OF  INFECTION 

perfectly  well  but  was  a  carrier,  probably  gave  diphtheria  to 
another  young  man  with  whom  he  slept. 

In  1897  a  mother  whom  I  saw,  stayed  for  a  few  days  in  a 
house  on  a  neighboring  street  taking  care  of  a  diphtheria 
case.  Soon  after  her  return  liome  her  son  was  taken  sick  with 
diphtheria,  and  when  cultures  were  taken  from  her  throat  she 
also  was  found  to  be  infected.^  In  1905  a  child  who  was  sent 
to  the  hospital  for  some  surgical  lesion  developed  scarlet 
fever  and  was  removed  to  the  scarlet-fever  ward.  Three  days 
after  his  return  home  another  child  in  the  family  was  taken 
sick  with  diphtheria,  and  a  few  days  later  a  culture  taken 
from  the  first  child  was  positive.^  Wesbrook^  reports:  "  Two 
alwaj'^s  well  children  carrying  bacilli  sent  home.  Diphtheria 
broke  out  shortly  after  their  arrival.  No  other  source  of 
infection  discovered.  One  always  well  girl  carrying  diph- 
theria bacilli  went  to  her  home.  Stepmother  and  children 
developed  diphtheria  within  a  few  days.  This  family  was 
practically  isolated  in  the  country." 

Hellstrom,^  during  a  diphtheria  outbreak  in  a  cavalry  regi- 
ment, noted  two  instances  in  which  perfectly  well  soldiers 
who  had  diphtheria  bacilli  on  their  mucous  membrane  car- 
ried the  disease  to  others.  Aaser  '  reports  a  child  with  diph- 
theria germs  taking  the  disease  home  from  a  scarlet-fever 
ward  where  there  was  a  diphtheria  outbreak. 

In  1906  at  Birmingham  "  there  was  a  milk  outbreak  of 
diphtheria  of  13  cases  due  to  infection  of  the  milk  by  the 
milk  handlers,  who  had  diphtheria  bacilli  in  their  throats,  but 
were  not  sick.  As  soon  as  they  were  isolated  the  outbreak 
ceased.    Similar  milk  outbreaks  caused  by  infected  well  per- 

'  Rep.  Supt.  Health,  Pmv.,  1897,  21. 

2  R(>p.  Supt.  Health,  Prov.,  190.'"),  .32. 

'  Prelim.  Rep.  on  Diphtheria  in  Well  Persons,  J.  Mass.  Ass.  Bds. 
Health,  Bost.,  1901,  XI,  10. 

«  Hellstrom,  cited  by  Fibiger,  B(>rl.  klin.  Wchnschr.,  1897,  XXXIV, 
753. 

*  Aaser,  Deutsche  rned.  Wehnschr.,  1895,  XXI,  357. 

"  Rep.  Med.  Off.  Health,  Binninghani,  190G,  40. 


CARRIERS  AND  MISSED  CASES  97 

sons  have  been  reported  from  Fitchburg/  Lowell,^  Brookline,^ 
Montclair,  N.  J.,*  Oroville,  Cal.,^  Australia*'  and  other  places. 

At  the  Willard  State  Hospital  '  a  watchman,  who  lived 
with  his  son-in-law  in  the  village,  who  had  diphtheria,  was 
never  sick  but  was  a  carrier.  He  played  cards  with  two 
clerks,  and  they  all  drank  from  the  same  pitcher.  The  clerks, 
who  had  not  been  exposed  to  diphtheria,  were  a  week  later 
taken  sick  with  the  disease.  Four  other  instances  of  infection 
by  carriers  occurred  during  the  same  outbreak,  and  a  similar 
instance  some  years  before. 

In  Lagrange  Co.,  Ind.,^  in  1902,  there  were  three  outbreaks 
in  a  school,  apparently  caused  by  the  teacher,  in  whose  nose 
diphtheria  bacilli  were  found,  and  who  had  shown  no  symp- 
toms but  a  slight  cold.  In  Boston^  a  boy  who  had  recovered 
from  diphtheria,  escaped  from  isolation  and  went  to  Brock- 
ton, and  within  four  days  three  clinical  cases  developed  in  the 
house  where  he  visited.  Fischer  ^'^  reports  an  outbreak  traced 
to  a  restaurant  in  which  were  several  carriers  and  mild  sore 
throats.  Solberg^i  had  a  boy  who  caused  several  cases  of  the 
disease.  He  had  been  kept  in  the  hospital  for  several  months, 
but  was  finally  discharged  with  the  bacilli  present.  Cob- 
bett's*^  outbreak  in  Cambridge  was  due  to  a  boy  apparently 

'  Prelim.  Rep.  on  Diphtheria  in  Well  Persons,  J.  Mass.  Ass.  Bds. 
Health,  Bost.,  1901,  XI,  9. 

2  Rep.  Bd.  Health,  Lowell,  1904,  24. 

^  Prelim.  Rep.  on  Diphtheria  in  Well  Persons,  J.  Mass.  Ass.  Bds. 
Health,  Bost.,  1901,  XI,  9. 

^  Pediatrics,  N.  Y.,  1901,  XII,  366. 

^  Rep.  St.  Bd.  Health,  Cal.,  1906-08,  198. 

^  Armstrong,  Austral.  M.  Gaz.,  Melbourne,  1908,  XXVII,  350. 

^  Report  of  Epidemic  of  Diphtheria  at  Willard  State  Hospital  by 
Russell  and  Salmon  [Rep.  State  Com.  on  Lunacy,  XVI],  35  of  Reprint. 

'  Letter  from  Dr.  H.  N.  Hurty,  Sec.  Ind.  St.  Bd.  Health,  1907. 

*  Prelim.  Rep.  on  Diphtheria  in  Well  Persons,  J.,  Mass.  Ass.  Bds. 
Health,  Bost.,  1901,  XI,  9. 

'"  Fischer,  Miinchen  med.  Wchn.schr.,  1906,  LIII,  250,  314. 
"  Solberg,  quoted  in  Pub.  Health,  Lond.,  1902-03,  XV,  515. 
''  Cobbett,  J.  Hyg.,  Cambridge,  1901,  I,  229. 


98  THE  SOURCES  AND  MODES  OF  INFECTION 

well,  but  who  for  some  weeks  had  had  a  sHght  nasal  discharge 
in  which  diphtheria  germs  were  present.  WilUams  ^  notes  a 
case  in  which  a  teacher  was  infected  with  clinical  diphtheria 
by  the  nasal  discharge  of  a  pupil  containing  atypical  bacilli.^ 
Newsholme  ^  saw  a  case  of  diphtheria  in  February,  1901, 
which  had  ear  discharge  for  a  short  time  only.  Suppuration 
recurred  April,  1904,  and  diphtheria  germs  were  present. 
Three  cases  of  the  disease  occurred  in  the  family  soon  after. 
The  ear  again  discharged  in  March,  1906,  with  bacilli  pres- 
ent, and  a  sister  apparently  contracted  the  disease  from  this 
source.  Newsholme  had  a  similar  case  in  1907.  Vance  ^ 
states  that  a  nurse  had  diphtheria  in  June,  and  after  one 
negative  culture  from  the  throat,  went  home  and  infected  3 
persons.  In  August  she  returned  to  the  hospital  and  infected 
4  other  persons,  at  Avhich  time  a  culture  from  throat  and  nose 
was  negative.  Subsequent  cultures  proved  positive,  and 
continued  so  until  late  in  November.  Strain^  also  reports  a 
nurse  in  whose  nose  diphtheria  bacilli  were  found  intermit- 
tently for  nine  months,  but  they  were  never  present  in  the 
throat.  Edsall  *'  notes  five  outbreaks  due  to  carriers,  and 
Solis-Cohen'  seven  such  outbreaks.  Cameron^  reports  that 
in  70  instances  cases  of  scarlet  fever  discharged  from  the  Lon- 
don hospitals  carried  diphtheria  to  their  homes,  and  that  in 
many  of  these  carriers  diphtheria  bacilli  were  shown  to  be 
present. 

Similar  cases  in  which  clinical  diphtheria  is  apparently  con- 
tracted from  perfectly  well  convalescents  or  carriers,  or  from 
slight  unnoticed  sore  throat,  or  from  rhinitis,  are  found  scat- 

1  Willi;uns,  J.  Larynsol.*  Lond.,  1905,  XX,  591. 

'  Wchbrook's  D'D^. 

■'  Newsholme,  Rep.  Med.  Off.  Health,  liriKhton,  190G,  13. 

*  Vance,  Intercolon.  M.  J.  Australas.,  Melbourne,  1908,  XIII,  152. 

'  Strain,  Lancet,  Lend.,  1908,  II,  1143. 

"  Ed.sall,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  125. 

'  Sf)lis-(;ohen,  J.  Am.  M.  A.ss.,  Chicago,  1909,  LII,  111. 

"  ('ameron,  Hep.  to  Asylums  Bd.  on  Return  Cases  of  Scarlet  Fever 
in  London,  1 901 -02,   II. 


CARRIERS   AND  MISSED  CASES  99 

tered  through  medical  hterature,  and  a  number  of  such  have 
been  collected  by  the  Massachusetts  Association  of  Boards 
of  Health,^  Nuttall  and  Graham-Smith,^  Newsholme/  Sit- 
tler/  Niven,^  Schneider,*'  myself  ^  and  others. 

Chronic  Diphtheria.  —  Diphtheria  sometimes  assumes  a 
chronic  form,  with  few  constitutional  symptoms,  and  little 
that  is  noticeable,  and  nothing  that  is  characteristic  in  the 
fauces.  This  condition  may  continue  for  months,  and  is 
sometimes  accompanied  by  considerable  antitoxin  in  the 
blood.    Such  cases  may  cause  typical  diphtheria.^ 

Glanders.  —  According  to  veterinary  writers  ^  the  infec- 
tion of  glanders  often  remains  latent,  and  also  many  mild 
chronic  cases  occur  which  are  the  source  of  considerable  out- 
breaks. The  Bureau  of  Animal  Industry  ^^  reports  an  instance 
where  a  horse  was  apparently  infectious  for  eight  years  with- 
out manifesting  any  symptoms  which  would  lead  even  an 
expert  to  suspect  the  infection.  Another  instance  was  given 
of  a  year-long  infection  of  an  apparently  well  animal. 

Influenza.  —  The  rapidity  with  which  epidemic  influenza 
spreads,  its  sudden  contemporaneous  appearance  at  many 
distant  points,  and  the  difficulty  of  tracing  the  route  of  infec- 
tion, render  it  almost  certain  that  there  must  in  this  disease 
be  many  mild  atypical  cases,  and  many  persons  infected,  but 
showing  no  symptoms.     That  the  disease  is  not  carried  by 

1  Prelim.  Rep.  on  Diphtheria  Bacilli  in  Well  Persons,  J.  Mass.  Ass. 
Bds.  Health,  Bost.,  1901,  XI,  9. 

^  Nuttall  and  Graham-Smith,  The  Bacteriology  of  Diphtheria,  Cam- 
bridge, 1908,  311. 

^  Newsholme,  Address  at  Victoria  Univ.,  Manchester,  Mar.  9,  1904, 
and  Med.-Chir.  Tr.,  Lond.,  1904,  LXXXVII,  549. 

*  Sittler,  Miinchen  med.  Wchnschr,  1906,  LIII,  863. 

*  Niven,  Rep.  on  the  Health  of  Manchester,  1908,  204.    ' 
«  Schneider,  Ztschr.  f.  Med.-Beamte,  Berl.,  XX,  698. 

'  Rep.  Supt.  Health,  Prov.,  1897,  19;  1898,  23;  1905,  32. 

*  Neisser  and  Kahnert,  Deutsche  med.  Wchnschr.,  1900,  XXVI, 
525,  and  Neisser,  Deutsche  med.  Wchnschr.,  1902,  XXVIII,  719. 

*  Law,  Text-Book  of  Veterinary  Medicine,  Ithaca,  1902,  IV,  235. 
"  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Circ.  No.  78,  4. 


100        THE  SOURCES  AND  MODES  OF  INFECTION 

the  air  over  long  distances,  as  has  been  urged  by  many,  but 
is  invariably  transmitted  by  persons,  has  been  shown  by  Par- 
sons, Schmid  and  others.  That  these  persons  often  show  no 
symptoms,  and  are  not  suspected  of  being  carriers,  also  seems 
certain. 

There  is  some  bacteriological  evidence  of  this,  but  the  bac- 
teriologists have  not  given  to  the  study  of  this  disease  the 
attention  which  it  deserves.  Finkler  found  the  bacillus  in 
the  sputum  a  year  after  the  beginning  of  an  attack.  Lord,^ 
during  non-epidemic  periods,  in  examining  cases  of  what 
appeared  ordinary  cough,  found  influenza  bacilli  present  in 
60  per  cent  of  the  cases.  Later,^  in  186  non-tuberculous  cases, 
mostly  bronchitis,  he  found  the  bacillus  frequently  present, 
often  in  almost  pure  culture.  Boggs^  has  also  found  chronic 
cases  somewhat  simulating  tuberculosis,  in  one  instance  last- 
ing for  a  year.  Holt,*  in  the  Babies'  Hospital  in  New  York, 
obtained  112  positive  cultures  out  of  312  taken  from  198 
persons.  Of  48  healthy  persons  16  yielded  positive  cultures. 
I  have  found  scarcely  any  other  reports  of  the  examination 
of  well  persons  for  this  organism,  but  the  frequency  with 
which  it  is  found  in  those  sick  with  other  diseases  is  evidence 
of  the  widespread  distribution  of  the  bacillus.  Wollstein,^  by 
swabbing  the  throat,  found  the  bacillus  in  16  of  37  cases 
of  pneumonia,  in  11  of  34  of  bronchitis,  in  8  of  18  cases  of 
measles,  in  8  of  16  of  tuberculosis,  but  only  5  times  in  65  cases 
of  other  diseases.  Davis  ®  found  influenza-like  bacilli  in  normal 
throats,  and  in  61  of  68  cases  of  whooping  cough  and  in  13 
of  23  cases  of  measles.  Inoculated  on  the  mucous  surface  of 
a  healthy  young  man,  fever  and  catarrhal  symptoms  devel- 
opetl.     Both  Davis  and  Wollstein  consider  that  the  so-called 

1  Lord,  Boston  M.  &  S.  J.,  1902,  CXLVII,  662. 

2  Lord,  Boston  M.  &  S.  J.,  1905,  CLII,  574. 

'  BoKKs,  Am.  J.  M.  Sc,  Phila.,  1905,  n.  8.,  CXXX,  902. 

*  Holt,  Am.  J.  Obst.,  N.  Y.,  1909,  LX,  343. 

s  Wollstein,  J.  Exper.  M.,  N.  Y.,  1906,  VIII,  681. 

"  Davis,  J.  Am.  M.  Ass.,  Chicago,  1907,  LXVIII,  1563. 


CARRIERS  AND   MISSED  CASES  101 

pseudo-influenza  bacilli  in  their  different  forms  are  of  the 
same  "  species  "  as  the  typical  forms.  Others  have  found 
the  bacillus  in  other  infectious  diseases,  as  Leibscher  ^  and 
Auerbach,"  the  latter  of  whom  obtained  it  in  5.4  per  cent  of 
700  cases  of  diphtheria,  scarlet  fever,  etc. 

The  Coccus  of  Pneumonia.  —  That  the  pneumococcus  is 
present  in  the  saliva  of  normal  mouths  was  early  recognized 
by  Pasteur,  Sternberg,  Welch  and  others,  and  is,  of  course,  a 
now  well-established  fact.  Recently  a  number  of  careful 
observations  have  been  made  to  determine  the  frequency  of 
its  occurrence,  its  virulence,  and  variations  in  form  and  habits 
of  growth.  Buerger^  found  it  present  in  50  per  cent  of  78 
normal  mouths,  and  in  34.8  per  cent  of  204  normal  throats 
not  so  carefully  examined.  He  also  found  that  it  could  be 
recovered  for  weeks  from  convalescents.  Of  the  cultures  from 
normal  mouths  79  per  cent  proved  virulent.  Hiss*  found  it 
in  14  of  22  persons,  and  Duval  and  Lewis  ^  in  all  of  24  per- 
sons about  the  laboratory.  Longcope  and  Fox^  obtained  it  in 
40  per  cent  to  50  per  cent  of  mouths  examined.  It  was  more 
often  found  and  more  virulent  in  winter.  Frost,  Divine  and 
Reineking  ^  found  it  in  36  per  cent  of  healthy  mouths,  23  per 
cent  in  autumn,  43  per  cent  in  winter  and  50  per  cent  in  the 
spring.  The  organism  may  persist  in  the  same  individual 
for  months.  Park  and  "Williams  ^  report  the  pneumococcus 
as  prevalent  both  in  city  and  country,  as  do  others,  but  note 
that  germs  from  normal  mouths  are  less  virulent  for  rabbits 

1  Leibscher,  Prag.  med.  Wchnschr.,  1903,  XXVIII,  85. 

2  Auerbach,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1904, 
XLVII,  259. 

»  Buerger,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  497. 
*  Hiss,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  547. 
6  Duval  and  Lews,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  473. 
»  Longcope  and  Fox,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  430. 
'  Frost,  Divine  and  Reineking,  J.  Infect.  Dis.,  Chicago,  1905  [Suppl. 
No.  1],  298. 

"  Park  and  Wilhams,  J.  Exper.  M.,  N,  Y.,  1905,  VII,  403. 


102        THE  SOURCES  AND  MODES  OF  INFECTION 

than  those  from  cases  of  pneumonia.  Wells  ^  found  pneu- 
mococci  in  the  throat  or  upper  respiratory  passages  in  45  per 
cent  of  135  persons,  and  Besser  ^  found  them  in  14  per  cent 
of  the  noses  of  57  well  persons,  and  Hasslauer  ^  in  24  of  111 
normal  noses.  Ruediger  *  got  positive  results  in  90  per  cent 
of  51  normal  throats,  in  91.4  per  cent  of  71  scarlet  fever 
throats,  in  12  of  14  cases  of  measles,  and  in  8  of  9  cases  of 
tonsillitis,  or  pharyngitis. 

Gonorrhea.  —  That  gonorrhea  assumes  a  latent  form  in 
both  men  and  women,  showing  no  signs  whatever  for  con- 
siderable periods,  and  relapsing  into  a  subacute  or  even  acute 
condition  after  it  was  supposed  to  be  cured,  has  long  been 
known.  But  it  is  only  since  the  discovery  of  the  gonococcus 
that  the  latency  of  this  infection,  as  well  as  its  persistence, 
has  been  fully  appreciated,  just  as  it  has  only  been  the  rec- 
ognition of  this  coccus  which  has  shown  the  serious  patho- 
logical changes  in  important  organs  which  often  follow 
gonorrhea.  There  has  also  been  demonstrated  recently  the 
frequent  innocent  transmission  of  the  disease  among  young 
children.  All  the  text-books  and  monographs  dealing  with 
gonorrhea  dwell  on  these  facts,  and  refer  to  the  finding  of 
the  germ  in  cases  long  supposed  to  be  well,  and  to  its  per- 
sistence for  long  periods  of  time.^  A  physician  told  me  of  a 
case  lasting  from  the  third  year  of  life  to  the  twenty-eighth. 
Some  striking  instances  of  the  latency  of  gonorrhea  are  given 
by  Chapman,"  and  he  has  shown  me  records  of  many  more 
in  which  unsuspected  infection  had  lasted  for  many  years. 
The  same  author  states  that  the  gonococcus  may  be  encysted 

1  Wells,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  361. 

2  Besser,  Beitr.  z.  path.  Anat.  u.  z.  allg.  Path.,  Jena,  1889,  VI,  331. 
'  Hasslauer,  Centralbl.  f.  Bakteriol.  [etc.],  Ist  Abt.  Ref.,  Jena,  1905, 

XXXVII,  1. 

*  liuodiger,  J.  Am.  M.  Ass.,  Chicago,  190G,  XLVII,  1171 

6  Werthcim,  Arch.  f.  d.  Geburtsh.,  Jena,  1902,  XLII,  192. 

«  Chapman,  Fiske  Fund  Prize  Essay,  Providence,  1905,  The  Sequelae 

of  Gonorrhea,  etc.,  31. 


CARRIERS  AND  MISSED  CASES  103 

or  dormant  in  tubal  or  ovarian  tissue  indefinitely.  Rathbun 
and  Dexter  ^  from  a  clinical  and  careful  bacteriological  study 
of  cases  show  that  infection  often  persists  long  after  the 
patient  is  apparently  cured,  and  that  such  uncured  cases  are 
far  more  common  than  is  generally  believed.  Hamilton^ 
refers  to  the  difficulty  of  demonstrating  the  coccus  in  mild 
and  chronic  cases,  and  states  that  such  cases  are  very  com- 
mon. Nottshaft  ^  followed  120  cases  of  gonorrhea  and  ob- 
tained the  gonococcus  from  73  per  cent  during  the  second 
six  months.  During  the  fourth  six  months  the  percentage 
fell  to  18,  and  in  the  third  year  the  gonococci  still  per- 
sisted in  6  per  cent  of  the  cases.  This  latency  is  the  chief 
cause  of  innocent  marital  infections.  It  is  also  one  reason 
why  the  medical  supervision  of  prostitution  can  never 
have  much  effect  in  restricting  the  disease.  No  practicable 
amount  of  inspection  would  ever  guarantee  freedom  from 
infection. 

Tubercle  Bacilli  in  Mouth  and  Nose.  —  There  are  two 
conditions  under  which  tubercle  bacilli  may  exist  in  human 
beings  without  appreciable  symptoms. 

First,  they  may  be  found  on  the  mucous  surfaces  of  mouth, 
throat,  or  nose.  Straus  *  examined  the  nose  of  29  well  per- 
sons, orderlies,  nurses  and  physicians  about  tuberculosis 
wards,  and  recovered  tubercle  bacilli  from  9.  Cornet  found 
them  in  his  own  nose.^  Jones,®  by  inoculating  animals  with 
mucus  from  the  nose  of  31  persons  not  brought  into  par- 
ticularly close  contact  with  consumptives,  demonstrated  the 
presence  of  tubercle  bacilli  in  11.    Similar  results  have  been 

1  Rathbun  and  Dexter,  N.  York  M.  J.  [etc.],  1909,  XC,  241. 

2  Hamilton,  J.  Infect.  Dis.,  Chicago,  1908,  V,  134. 

'  Nottshaft,  Die  Chronische  Gonorrhea  der  Miinsliche  Harnrohre, 
Leipzig,  1905. 

*  Straus,  Arch,  de  med.  exper.  et  d'anat.  path.,  Par.,  1894,  VI,  633. 

'  Cornet,  Nothnagels  Encyclopedia,  Phila.  and  Lond.,  1907,  Tuber- 
culosis, 152. 

•  Jones,  Med.  Rec,  N.  Y.,  1900,  LVIII,  285. 


104       THE  SOURCES  AND  MODES  OF  INFECTION 

reported  by  Moller  ^  and  Bernheim.^  Persons  in  the  vicinity 
of  consumptives  must,  unless  great  care  be  taken,  receive  a 
certain  number  of  tubercle  bacilli  upon  their  mucous  sur- 
faces. Whether  they  increase  in  numbers  in  such  a  location 
is  not  shown  by  the  observers  quoted,  but  unless  they  do  it 
seems  rather  surprising  that  they  can  be  demonstrated  in 
such  a  proportion  of  cases.  On  the  other  hand,  it  does  not 
seem  likely  that  conditions  in  the  mouth  and  nose  are  favor- 
able for  the  growth  of  this  bacillus,  and  the  weight  of  evi- 
dence seems  to  be  that  the  tubercle  bacillus  does  not,  to  any 
extent  at  least,  develop  on  the  normal  mucous  membrane 
of  the  throat  or  nose  of  well  persons. 

Blair  ^  reports  finding  tubercle  bacilli  in  the  nose  of  various 
wild  animals  in  captivity. 

Latent  Tuberculosis.  —  That  the  tubercle  bacilli  invade 
the  tissues  and,  creating  little  disturbance,  remain  latent  for 
a  considerable  period  of  time,  has  been  amply  demonstrated. 
While  there  are  not  many  who  believe  that  this  latency  is 
so  universal  or  so  persistent  as  does  von  Behring,  yet  it  is 
certainly  not  a  rare  phenomenon.  L.  Rabinowitsch*  in  a 
recent  article  gives  a  short  resume  of  the  work  of  various 
observers,  and  Harbitz  ^  has  also  discussed  it  in  an  article 
on  tuberculosis  of  children.  Harbitz,  in  142  autopsies  of  chil- 
dren who  were  clinically  free  from  tuberculosis,  and  in  whose 
glands  no  macroscopic  or  microscopic  signs  of  the  disease 
could  be  seen,  nevertheless  was  able  by  inoculation  to  dem- 
onstrate the  presence  of  virulent  tubercle  bacilli.  Rabino- 
witsch  reports  four  cases  of  virulent  Ijacilli  in  lymph  glands 
that  had  undc^rgone  calcareous  degeneration,  thus  indicating 
a  long-standing  latency.    Many  similar  observations  by  other 

'  Moller,  Ztschr.  f.  Hyg.  u.  Infectionskrankli.,  Lcipz.,  1899,  XXXII, 
205. 

^  Bernheim,  Cliniquo,  Brux.,  1905,  XIX,  346. 
'  Blair,  J.  Comp.  M.  &  Vet.  Arch.,  1903,  XXIV,  278. 
*  Ral)inowitscIi,  Horl.  klin.  W(!hnschr.,  1907,  XLIV,  35. 
^  Harbitz,  J.  Infect.  Dis.,  Chicago,  1905,  II,  143. 


CARRIERS  AND  MISSED  CASES  105 

writers  are  given  by  those  just  quoted,  and  Gaffky '  has 
recently  reported  finding  the  glands  of  11  per  cent  of  246  well 
persons  as  containing  living  bacilli,  demonstrated  by  inocu- 
lation tests.  Tubercle  bacilli  are  found  in  the  tonsils  as  well 
as  in  the  Ijinph  glands.  Lartigau  and  Nicoll  ^  found  infected 
adenoids  in  12  of  75  healthy  children,  and  Weichselbaum  and 
Bartel,^  Goodale  *  and  Cornet "  report  similar  findings. 

Leprosy.  —  Sticker  ^  says  that  lepra  bacilli  often  remain 
latent  in  the  nose  for  long  periods. 

Bacteria  of  Suppuration,  Latency.  —  As  has  been  stated  on 
page  20,  pus  bacteria  are  normal  inhabitants  of  the  skin  and 
mucous  surfaces,  and  may  even  invade  the  glands  and  other 
deeper  tissues  and  remain  latent  for  long  periods  of  time. 
They  may  later,  as  the  result  of  traumatism,  be  carried  by 
the  circulation  to  distant  organs,  there  causing  suppuration.^ 
Among  those  who  have  demonstrated  the  latency  of  infection 
with  pus-forming  bacteria  may  be  mentioned  Manfredi  and 
Viola,^  Kalble,^  Perez  ^°  and  Hess."  Conradi  ^^  seems  to  have 
employed  an  improved  technique  in  his  work,  and  has  demon- 
strated bacteria  in  72  of  162  apparently  healthy  organs  taken 

1  Gaffky,  Konferenz  Internat.  f.  Tuberk.,  Wien,  1907. 
^  Lartigau  and  Nicoll,  Am.  J.  M.  Sc,  Phila.,  1902,  n.  s.,  CXXIII, 
1031. 

»  Weichselbaum  and  Bartel,  Wien  klin.  Wchnschr.,  1905,  XVIII,  241. 

*  Goodale,  Boston  M.  &  S.  J.,  1906,  CLV,  278. 

^  Cornet,  Nothnagels  Encyclopedia,  Phila.  and  Lond.,  1907,  Tuber- 
culosis, 158. 

*  Sticker,  Arb.  a.  d.  k.  Gesndhtsamte.,  Berl.,  1899,  XVI,  Anlage  I. 
^  Soprano,  Centralbl.  f.  Bakteriol.  [etc.],  1st  Abt.  Orig.,  Jena,  1906, 

XLI,  601. 

*  Manfredi  and  Viola,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz., 
1899,  XXX,  64. 

"  Kalble,  Miinchen  med.  Wchnschr.,  1899,  XLVI,  622. 

*"  Perez,  Jahresb.  u.  d.  Fortschr.  .  .  .  d.  path.  Mik.  Baumgarten, 
1897,  XIII,  894. 

"  Hess,  Centralbl.  f.  Bakteriol.  [etc.],  1st  Abt.  Orig.,  Jena,  1907, 
XLIV,  1. 

''  Conradi,  Munchen  med.  Wchnschr.,  1908,  LV,  1523. 


106       THE  SOURCES  AND  MODES  OF  INFECTION 

from  150  healthy  animals.  Ford'  and  Dudgeon^ also  report 
finding  bacteria,  especially  pus-forming  types,  lying  latent  in 
healthy  organs.  Bardley^  found  bacteria  pathogenic  for 
rabbits  in  196  of  200  atrophied  tonsils,  and  in  101  he  demon- 
strated Streptococcus  pyogenes. 

Latent  Tetanus.  —  Canfora  *  and  Vincent  ^  have  both 
shown  that  tetanus  spores  may  be  injected  into  the  body 
and  remain  latent  for  some  time.  Tetanus  occasionally 
develops  in  an  inexplicable  manner  after  surgical  opera- 
tions and  under  certain  other  conditions,  as  following  the 
administration  of  hypodermic  injections  of  the  salts  of 
quinia.  Semple  ^  has  recently  studied  this  subject  in  a 
most  careful  manner.  He  finds  that  washed  spores  of 
tetanus  when  injected  into  test  animals  do  not  cause  the 
disease,  and  may  remain  latent  and  virulent  for  as  long  as 
7  months.  Injections  of  the  salts  of  quinia  will  in  such 
animals  give  rise  to  tetanus  by  the  injurious  effects  of  the 
solution  upon  the  tissues.  It  may  be  that  surgical  opera- 
tions may  sometimes  operate  in  the  same  way  to  favor  the 
development  of  latent  spores.  It  has  been  suggested  that 
the  relapses  which  arc  sometimes  noted  in  tetanus  are  due 
to  the  persistence  of  foci  of  latent  infection.  Semple  found 
tetanus  bacilli  in  the  intestines  of  4  of  10  healthy  human 
Ijeings,  and  in  3  they  proved  virulent  for  guinea  pigs. 

Likeness  of  Scarlet  Fever  and  Diphtheria. — Unfortunately 
we  do  not  know  the  nature  of  scarlet  fever  virus,  hence  many 
important  matters  relating  to  the  causation  of  this  disease 

1  Ford,  J.  Hyg.,  Gambridgc,  1901,  I,  277. 

2  Dudgeon,  Lancet,  Lond.,  1908,  II,  1651. 

3  Bardley,  Johns  Hopkins  llosp.  Bull.,  Bait.,  1909,  XX,  88. 

<  Canfora,  Ccntralbl.  f.  Baktcriol.  [etc.],  I  Abt.  Orig.,  Jena,  1907, 
XLX,  495. 

^  Vincent,  J.  de  physiol.  ct  de  path.  g<5n.,  Par.,  1908,  X,  664. 

«  Soinplc,  Sc.  Memoirs,  Med.  and  San.  Dept.,  Gov.  India,  1911, 
XLIII. 


CARRIERS  AND  MISSED  CASES  107 

are  in  doubt.  There  are  many  points  of  resemblance  between 
this  disease  and  diphtheria,  such  as  the  degree  of  infective- 
ness,  the  apparent  variation  in  the  period  of  incubation  and 
duration  of  infection,  the  very  brief  incubation  in  some  cases, 
the  persistence  of  infection  in  some  instances  long  after  recov- 
ery and  the  contrary  fact  of  the  early  loss  of  infectivity  in 
many  instances,  the  prominence  of  the  initial  throat  symp- 
toms, and  the  occurrence  of  albuminuria  and  middle  ear 
inflammations.  We  are  justified,  I  think,  in  looking  for  a  bac- 
terial infection,  and  the  probability  is  that  scarlet  fever  is 
in  the  main,  like  diphtheria,  a  local  disease  of  the  mucous 
surfaces,  chiefly  of  the  throat  and  nose.  We  certainly  see 
many  mild  atypical  cases  of  scarlet  fever  just  as  we  do  of 
diphtheria,  probably  fully  as  many,  and  we  naturally  expect 
to  find  also  true  carriers  who  exhibit  no  symptoms  at  all. 

Atypical  Scarlet  Fever.  —  As  the  bacteriologist  cannot  help 
us,  we  have  to  rely  on  clinical  evidence,  which  is  much  more 
uncertain  and  diflEicult  to  secure.  The  la^Tiian  and  the  inex- 
perienced physician  are  apt  to  scoff  at  the  suggestion  of  scarlet 
fever  unless  the  patient  has  a  high  fever  and  is  as  red  as  a 
lobster.  But  all  who  have  seen  much  of  this  disease  know 
that  it  is  exceedingly  common  to  see  cases  with  a  scarcely 
discernible  indefinite  rash  lasting  for  only  a  few  hours,  a  rise 
in  temperature  of  only  a  degree  or  two  lasting  also  only  a 
few  hours,  and  the  merest  trace  of  sore  throat.  Sometimes 
the  rash  may  be  entirely  absent  and  even  the  fever  may 
escape  the  most  careful  observation. ^  In  institutions  and 
families,  such  cases,  considered  doubtful  at  first,  or  perhaps 
entirely  neglected,  prove  to  be  the  origin  of  typical  symptoms 
in  others.  Every  health  officer  will  recall  many  such  cases. 
They  are  the  missed  cases  which  are  such  a  factor  in  the 
maintenance  of  this  disease.  There  are  many  references  to 
them  in  the  reports  of  health  officers  and  in  medical  litera- 
ture.   Among  others  who  report  such  atypical  cases  are  News- 

1  Caziot,Bull.  et  mem.,  Soc.  med.d.  hop.  de  Par.,  1903,  n.s.,  XX, 799; 
Semaine  med.,  Par.,  1903,  XXIII,  205. 


108       THE  SOURCES  AND  MODES  OF  INFECTION 

holme,^  Caziot,^  Welch  and  Schamberg,^  Cameron/  Butler,^ 
Lesarge,^  Thresh/  Corlett/  Liidke/  Kerley/"^  and  Thorn- 
ton and  Milder  referred  to  below.  In  most  of  these  missed 
cases  there  were  some  slight  symptoms,  though  overlooked 
or  misunderstood  at  the  time.  In  Manchester,  in  1906, 
there  were  discovered  229  missed  cases,  mostly  of  a  mild 
character.     From  these  139  other  cases  had  developed. ^^ 

Number  of  Atypical  Cases.  —  It  is  difficult  to  estimate  the 
number  of  atypical  cases  of  scarlet  fever.  Probably  it  varies 
according  to  the  extent  and  severity  of  the  outbreak,  and 
for  other  reasons.  Newsholme^^  has  reported  a  milk  out- 
break in  which  the  number  of  sore  throats  without  the  pres- 
ence of  eruption  was  215,  while  the  number  of  typical  cases 
of  scarlet  fever  was  only  38.  Butler,^^  at  Wellesden,  studied 
the  incidence  of  sore  throat  in  families  where  there  was  re- 
ported scarlet  fever,  and  found  that  31.2  per  cent  of  1266 
persons  in  such  families  had  sore  throats,  while  only  2.8  per 
cent  of  1644  persons  living  in  families  where  there  was  no 
scarlet  fever  had  sore  throat.  In  a  school  with  300  children 
Thornton ^^  found  31  typical  cases,  19  cases  with  no  rash  and 
slight  sore  throat,  and  46  cases  in  which  only  desquamation 

»  Newsholme,  Tr.  Med.-Chir.  Soo.,  Glasg.,  LXXXVII,  549. 

2  Caziot,  Bull,  et,  m6in.,  Soc.  mcd.  d.  hop.  de  Par.,  1903,  n.  s.,  XX, 
799;  Semaino  mod.,  Par.,  1903,  III,  20.5. 

^  Welch  and  Schamberg,  Acute  Infectious  Diseases,  Phila.,  1905, 
390. 

*  Cameron,  Rep.  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria 
to  Asylums  Bd.,  Lond.,  1901-02,  38,  7S. 

6  Butler,  Proc.  Roy.  Soc.  Med.,  Lond.,  1908,  I,  Epidemiol.  Sec,  225. 

»  Gaz.  d.  hop.,  Par.,  1909,  LXXXII,  1471. 

'  Med.  Officer,  1910,  IV,  5. 

8  J.  Am.  M.  Ass.,  Chicago,  1910,  LV,  195. 

9  Med.  Klin.,  Berl.,  1911,  VII,  127. 
'»  Am.  J.  Dis.  Child.,  1911,  I,  71. 

"  Rep.  on  Health  of  Mantiliester,  190G,  43. 

••^  Newslioltne,  Rep.  Med.  Off.  Ilealtli,  Brighton,  1906,  48. 

'^  liutler,  Rep.  Med.  Oflf.  Health,  W.'UcsdcMi,  1907,  76. 

"  Thornton,  Brit.  M.  J.,  Lond.,  1908,  I,  495, 


CARRIERS  AND  MISSED  CASES  109 

was  noticed.  Mader  ^  observed  9  typical  and  12  very  atypi- 
cal cases  in  an  outbreak  in  a  home  for  epileptics.  Ewart,^ 
from  an  examination  of  8000  school  children  at  Middle- 
borough,  estimates  that  there  must  be  at  least  3  missed  cases 
annually  for  each  1000  children.  True  "  carriers,"  that  is, 
perfectly  well  persons,  are  sometimes  reported.  Thus  I 
have  noted  an  instance  where  a  woman  apparently  in  this 
way  carried  scarlet  fever  to  her  child.  She  had  been  taking 
care  of  another  child,  and  after  an  entire  change  of  clothing, 
bath  and  shampoo,  visited  the  first-named  child,  who  was 
taken  sick  two  days  later.  Newsholme  reports  what  he 
thinks  are  possibly,  or  even  probably,  similar  cases.  New- 
man,^ of  Finsbury  (London),  noted  5  carriers  among  school 
children,  three  of  whom,  though  they  had  never  had  the 
disease,  transmitted  it  to  others.  Kerr  ^  also  reports  5  such 
cases.  When  a  diphtheria  patient  discharged  from  a  hospi- 
tal carries  scarlet  fever  home  to  his  family,  he  must  in  most 
instances  be  considered  a  true  carrier,  for  it  is  unlikely  that 
symptoms  of  scarlet  fever  would  often  escape  notice  in  the 
hospital.  Ten  of  this  sort  of  return  carriers  are  reported  by 
Simpson,^  30  by  Cameron  ®  and  44  by  Turner.^ 

Smallpox.  —  There  is  still  doubt  as  to  the  specific  cause 
of  smallpox.  The  claims  that  have  been  advanced  in  favor 
of  this  or  that  micro-organism  have  not  as  yet  been  substan- 
tiated. Hence  there  is  no  "  laboratory  "  evidence  that  car- 
riers of  this  disease  exist,  nor  is  there  much  clinical  evidence 

1  Mader,  Cor.-Bl.  f.  schweiz.  Aerzte,  1908,  XXXVIII,  169. 

2  Ewart,  Pub.  Health,  Lond.,  1910-11,  XXIV,  275. 

3  Newman,  Rep.  Med.  Off.  Health,  Lond.,  1904,  27. 

*  Kerr,  Rep.  Med.  Off.  Education,  Lond.,  1907,  43. 

*  Simpson,  Rep.  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria 
to  Asylums  Bd.,  Lond.,  1898-99,  8. 

*  Cameron,  Report  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria 
to  Asylums  Bd.,  Lond.,  1901-02,  43. 

^  Turner,  Rep.  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria  to 
Asylums  Bd.,  Lond.,  1902-04,  3. 


110       THE  SOURCES  AND  MODES  OF  INFECTION 

that  perfectly  well  persons  transmit  the  disease.  There  are, 
it  is  true,  scattered  through  medical  literature  numerous 
reports  of  instances  of  such  transmission.  These  reports,  as 
often  in  other  diseases,  are,  as  regards  the  evidence,  rather 
unsatisfactory.  There  is  usually  a  possibility  of  such  trans- 
mission, no  actual  demonstration.  Nevertheless  it  is  quite 
possible  that  there  may  be  true  carriers  of  smallpox,  and 
there  may  be  a  considerable  number  of  them.  Mild  cases 
are  often  very  numerous.  This  was  well  illustrated  in  the 
recent  epidemic  in  the  United  States  and  England.  In  the 
United  States  in  the  year  ending  June  30,  1901,  the  fatality 
in  38,506  cases  was  only  1.79  per  cent.  At  such  a  time  great 
numbers  of  cases  escape  recognition.  The  patients  often 
have  no  idea  that  they  are  sick  with  a  dangerous  disease. 
They  may  be  at  their  work  even  during  the  prodromal  stage. 
There  may  be  only  half  a  dozen,  or  even  fewer,  atypical 
pustules.  I  have  in  rather  a  limited  experience  seen  several 
such  cases.  They  are  also  reported  by  Welch  and  Scham- 
berg.^  These  authors  also  state  that  cases  occur  where  there 
is  no  eruption  at  all.  Davies  ^  reports  a  nurse  who  was 
exposed  to  smallpox  early  in  February  and  who  had  some 
fever  and  headache  without  any  eruption  or  other  symp- 
toms. Twelve  days  after  she  returned  to  her  ward  work, 
which  was  on  February  28th,  one  of  her  patients  in  the 
ward  developed  frank  smallpox.  Davies  from  epidemio- 
logical evidence  thinks  that  chronic  carriers  do  not  occur 
in  this  disease.  The  step  from  half  a  dozen  points  of 
eruption  to  none  at  all  is  so  slight,  and  the  extremely  mild 
cases  at  times  are  so  numerous,  that  a  considerable  number 
sine  eru'ptione  may  rcasona])ly  be  expected.  Armstrong  ^  re- 
cently reports  three  such  cases  with  some  fever  and  subjec- 
tive symptoms  but  no  eruption.  They  occurred  in  infected 
families  and  subsequently  proved  refractory  to  vaccination. 

*  Welch  and  RchambcrR,  Acuto  TnfootiouR  Disoasos,  Phila.,  1905,  207. 
2  i:)avi(;s,  Rnj).  Mod.  Off.  Iloaltli,  liristol,  1909,  24. 
'  Armstrong,  Arch.  f.  Diagnosis,  1909,  II,  126. 


CARRIERS  AND  MISSED  CASES  111 

Measles.  —  There  is  little  clinical  evidence  that  "carriers" 
of  measles  are  common.  Most  health  officers  consider  that 
measles  is  rarely  carried  by  a  "  third  person."  It  usually 
has  a  quite  definite  clinical  picture.  In  Aberdeen,  so  Dr. 
Matthew  Hay  writes  to  me,  judging  from  a  census  taken  in 
certain  schools,  it  was  estimated  that  from  90  to  93  per  cent 
of  the  children  over  ten  years  of  age  had  had  a  recognized 
attack  of  measles.  That  such  a  high  percentage  of  children 
had  recognized  attacks  indicates  that  atypical  cases  cannot 
be  very  common.  Mild,  atypical  and  unrecognized  cases  of 
this  disease  must  be  far  less  numerous  than  are  such  cases 
in  scarlet  fever,  diphtheria  and  typhoid  fever.  Levy  at 
Richmond  ^  investigated  2331  cases  during  an  outbreak. 
They  were  all,  without  exception,  traced  to  previous  frank 
cases  of  the  disease.  Levy  could  find  no  evidence  of  in- 
fection from  either  carriers  or  fomites.  His  careful  work 
in  the  study  of  this  outbreak  renders  his  conclusions  of  the 
highest  value. 

Protozoan  Diseases.  —  Although  the  marks  of  distinction 
between  animal  and  vegetable  life  as  seen  among  the  lower 
forms  are  ill  defined  and  uncertain,  yet  it  is  generally  agreed 
that  though  the  group  of  organisms  known  as  bacteria  have 
characters  belonging  to  both  the  vegetable  and  the  animal 
kingdom,  they  are  more  nearly  allied  to  the  former,  while  an- 
other group,  known  as  protozoa,  are  allied  to  the  lower  forms 
of  animal  life.  Although  one  of  the  latter  class  was  discovered 
to  be  the  cause  of  malaria  in  1880,  at  a  time  when  most  of  the 
disease-producing  bacteria  were  unknown,  the  bacteria  have 
received  far  more  study,  and  indeed  it  is  only  recently  that 
the  protozoa  as  the  cause  of  disease  have  received  much  at- 
tention. It  is  known  that  a  number  of  diseases  both  of  men 
and  of  animals  are  caused  by  protozoa  of  various  types. 
As  has  recently  been  emphasized  by  Daniels,^  latency  is  a 

1  Richmond  Rep.  Health  Dept.,  1910,  38. 

2  Daniels,  Brit.  M.  J.,  Lond.,  1909,  II,  767. 


112       THE  SOURCES  AND  MODES  OF  INFECTION 

common  phenomenon  of  protozoan  infection,  and  is  of  the 
utmost  importance  from  an  epidemiological  standpoint. 
Not  only  do  the  blood  parasites  maintain  long  continued  in- 
fection with  few  symptoms,  but  such  forms  as  Ameha,  Balan- 
tidium  and  Lamhlia  live  in  the  intestines  indefinitely,  repro- 
ducing themselves  asexually.  A  number  of  the  diseases  to 
be  referred  to  do  not  affect  man,  but  they  serve  to  illustrate 
the  prevalence  of  latency  in  protozoan  infections. 

Texas  Cattle  Fever.  —  It  has  long  been  recognized  that 
the  Texas  fever  of  cattle  could  be  transmitted  by  apparently 
healthy  animals.  The  explanation  of  this  fact  was  not,  how- 
ever, forthcoming  until  Smith  and  Kilborne's  ^  classical  re- 
searches in  1893  demonstrated  that  the  disease  was  due  to  a 
blood  parasite,  a  protozoan  (Piroplasma  higeminum) ,  not  a 
bacterium,  and  also  demonstrated  that  it  is  only  transmitted 
from  animal  to  animal  by  means  of  a  species  of  tick  (Boophi- 
lus  annulaius) ,  in  which  the  parasite  passes  through  a  cycle 
of  changes  necessary  for  the  maintenance  of  the  species.  This 
work  of  Smith  and  Kilborne's  was  one  of  the  most  important 
steps  in  the  development  of  our  knowledge  of  the  insect 
carriageof  disease,  a  knowledge  which  has  beenof  such  inesti- 
mable value  in  connection  with  malaria,  sleeping  sickness, 
yellow  fever  and  other  blood  diseases.  It  was  soon  deter- 
mined that  animals  which  had  recovered  from  Texas  fever 
and  were  immune  to  it,  carried  the  piroplasma  in  the  blood 
for  an  indefinite  time.  In  one  instance  it  was  known  to 
have  remained  for  thirteen  years.^  Reports  from  the  Philip- 
pines ^  show  that  many  of  the  cattle  in  those  islands  are  in- 
fected with  the  parasites  of  Texas  fever  though  showing  no 
symptoms.  Slightly  different  types  of  this  disease  occur 
among  cattle  in  Europe  and  in  Africa  caused  by  different 
species  of  piroplasma  and  spread  by  carriers. 

1  Smith  and  Kilborne,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Bull.  No.  1, 
1893,  57. 

2  U.  S.  Dri)t.  AKric,  llcp.  Bu.  An.  Ind.,  1904,  XXI,  26. 
»  Bull.  14,  Bu.  Gov.  Liib.,  Manila,  P.  I.,  1904,  11. 


CARRIERS  AND  MISSED  CASES  113 

Nagana.  —  Nagana  ^  is  an  African  cattle  disease  which, 
like  the  sleeping  sickness,  is  caused  by  a  trypanosome,  T. 
hrucei,  and  is  also  transmitted  by  a  tsetse  fly,  G.  7norsitans. 
Wild  herbivora  are  very  generally  infected,  but  because  of 
immunity,  probably  acquired,  they  show  few  or  no  symp- 
toms.    These  carriers  are  the  real  source  of  the  disease. 

Dourine.  —  This  is  a  contagious  disease  of  horses  spread 
almost  exclusively  by  the  sexual  act.  It  is  caused  by  a 
trypanosome,  T.  equiperdum,  found  in  the  secretions,^ 
b!ood  and  tissues.  Although  recovery  may  occur,  the 
trypanosomes  remain  for  months  in  the  sexual  organs  of 
apparently  cured  animals  and  thus  spread  the  disease. 

Malaria.  —  The  most  important  of  the  protozoan  diseases 
is  malaria.  It  had  always  been  believed  that  this  disease 
might  remain  latent  for  months  and  years,  but  what  latency 
really  meant  could  not  be  determined  until  after  the  dis- 
covery of  the  specific  cause  of  the  disease.  Many  of  the 
protozoa  pass  through  various  metamorphoses,  or  fixed  cycles 
of  development,  and  it  was  found  that  in  malaria  the  Plas- 
modium, which  is  its  cause,  may  in  certain  stages  persist  in 
the  blood  or  organs  of  the  body  without  causing  any  charac- 
teristic symptoms,  or  indeed  any  symptoms  at  all.  Then  at 
any  time,  from  one  cause  or  another,  its  reproduction  may 
again  become  active  and  more  or  less  marked  symptoms 
appear.  Thus  relapses  may  occur  after  a  period  of  several 
years,  when  the  bodily  resistance  is  from  any  cause  impaired. 
Thus  fever  after  surgical  operation  is  not  rarely  due  to  a 
latent  malaria  becoming  active,  the  parasite  being  found  in 
the  blood  and  the  symptoms  yielding  to  quinia.  As  malaria 
is  a  strictly  transmissible  disease,  the  Plasmodium  which 
causes  it  being  borne  from  one  person  to  another  by  mosqui- 
toes, a  latent  case  of  the  kind  described  may  be,  and  doubt- 
less often  is,  the  means  of  introducing  the  disease  into  hitherto 

^  Minchin,  Gray  and  Tullock,  Proc.  Roy.  Soc,  Lond.,  1906;  Nature, 
Lond.,  1906,  LXXVII,  57. 

2  U.  S.  Dept.  Ag.,  Bu.  An.  Ind.,  Bull.  No.  142,  1911. 


114       THE  SOURCES  AND  MODES  OF  INFECTION 

uninfected  localities.  Unless  such  cases  drift  into  hospitals, 
they  are  almost  certain  to  be  unrecognized.  Craig ^  made  a 
careful  study  of  424  such  latent  cases  found  among  1653  sol- 
diers examined  in  the  Philippines.  Since  I  first  wrote  this 
chapter  Craig's  book  has  appeared  in  which  he  discusses  in 
much  detail  latency  and  recurrences.^  He  has  noted  an  asex- 
ual conjugation  of  the  parasites  in  the  blood  cells,  which  is 
followed  by  a  resting  stage,  and  which  he  believes  has  some 
relation  to  the  latency  of  the  infection.  Where  malaria  pre- 
vails extensively,  as  in  the  tropics,  it  has  long  been  noticed 
that  a  large  part  of  the  adult  population  is  immune.  It  is 
now  known  that  this  immunity  is  to  a  large  extent  acquired, 
and  is  due  to  the  invasion  of  the  body  in  infancy  by  the 
parasites.  This  invasion,  while  sometimes  causing  symptoms 
and  death,  frequently  gives  rise  to  few  or  no  symptoms,  or 
if  some  reaction  appears  at  first,  it  soon  disappears,  and  the 
children  may  seem  perfectly  well  though  the  parasites  are 
constantly  found  in  the  blood.  They  disappear  year  by  year 
and  infection  is  rarely  found  after  adolescence.  Koch^  in 
Africa  found  large  numbers  of  children  infected,  even  as  high 
as  100  per  cent.  Plehn*  found  many  adults  infected  though 
not  sick.  Christophers  and  Stephens'^  found  the  parasites  in 
the  blood  of  90  per  cent  of  infants  examined  in  one  locality 
on  the  Gold  Coast  in  Africa,  and  the  Thompson  Yates  ex- 
pedition to  Nigeria"  reports  finding  them  in  63  per  cent  of 
children  under  3  years  of  age.  Ziemann^  found  that  in  the 
Cameroon  country  37  per  cent  of  children  under  5  years  of 

1  Craig,  J.  Infect.  Dis.,  Chicago,  1907,  IV,  108. 

2  The  Mahirial  Fevers,  N.  Y.,  1909,  228. 

'  Koch,  cited  in  Thompson  Yates'  Lab.  Rep.,  1900,  No.  4. 

*  Plehn,  cited  by  Marchiafava  and  Bignani,  Twentieth  Cent.  Prac- 
tice, XXI,  807. 

*  Christoplicrs  and  Stephens,  Reports  of  the  Malarial  Commission  of 
the  Roy.  Hoc.  (Eng.),  2nd  Ser.,  1900-03,  15. 

"  Thompson  Yates'  Lab.  Rep.,  1900,  III,  Ft.  2,  201. 

'  Deutsche  med.  Wchnschr.,  1900,  XXVI,  399,  C42,  753,  769. 


CARRIERS  AND  MISSED  CASES  115 

age  were  infected.  In  Panama  Kendall^  found  57  per  cent 
infected  of  the  natives  of  all  ages  examined  in  the  village 
of  Bahio,  and  73  per  cent  of  foreigners.  While  many  of 
the  latter  were  more  or  less  sick,  many  were  entirely  well. 
Darling^  in  villages  in  the  Panama  Canal  zone  where  there 
were  no  Anopheles,  nevertheless  found  that  10  per  cent  of 
the  laborers  at  work  were  infected  though  they  were  not  at 
all  sick.  Among  the  families  of  the  Spanish  and  the  West 
Indians,  the  latent  infection  reached  30  per  cent.  It  is  this 
latent  infection  in  the  blood  of  the  native  population  which 
is  the  cause  of  the  malaria  which  so  certainly  attacks  arrivals 
from  non-malarial  regions.  The  greater  the  distance  that  can 
be  placed  between  the  natives  and  the  strangers  the  less 
the  danger  of  the  latter  contracting  the  disease. 

Sleeping  Sickness.  —  African  sleeping  sickness  has  been 
shown  to  be  due  to  a  protozoan,  Trypanosoma  gamhiense. 
This  disease  has  been  much  studied  of  late,  and  it  seems  cer- 
tain that  it  is  transmitted  by  means  of  the  tsetse  fly  (Glossina 
palpalis),  though  whether  it  is  a  purely  accidental  mechanical 
transference  on  the  proboscis  of  the  fly,  or  whether  it  passes 
through  a  part  of  its  life  history  in  the  body  of  the  fly,  as 
the  Plasmodium  of  malaria  does  in  the  mosquito,  is  still  uncer- 
tain. In  any  event  the  parasite  is  frequently  found  in  the 
blood  of  apparently  healthy  subjects,  just  as  is  the  malarial 
parasite.  According  to  Todd  ^  it  may  remain  in  the  blood 
for  15  years,  causing  no  symptoms,  and  frequently  remains 
for  many  months.  The  expedition  from  the  Liverpool  School 
of  Tropical  Medicine*  found  many  natives  infected,  but  who 
exhibited  no  symptoms,  or  only  slight  symptoms.  The  greater 
the  prevalence  of  the  disease  the  more  common  are  these 
latent  cases.    In  Gambia,  where  the  disease  is  rare,  not  more 

•  Kendall,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVI,  1151,  1266. 
»  Darling,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIU,  2051. 

'  Todd,  Tr.  Epidemiol.  Soc,  Lond.,  1905-06,  XXV,  1. 

*  Liverpool  School  Trop.  Med.  Memoirs,  1904,  XIII;  Med.  News, 
N.  Y.,  1904,  LXXXV,  526,  615. 


116       THE  SOURCES  AND  MODES  OF  INFECTION 

than  one  native  in  1000  examined  showed  the  parasites, 
while  in  the  Congo  46  in  100  were  infected,  and  in  Uganda 
the  percentage  was  still  higher.  Whether  the  disease  is 
always  transferred  from  man  to  man,  or  whether  some  of 
the  lower  animals  also  harbor  the  parasites  and  thus  serve 
as  a  "  reservoir  "  from  which  the  human  disease  is  derived, 
is  as  yet  uncertain. 

Syphilis.  —  The  spirochete  of  syphilis  has  in  one  instance 
been  reported  as  remaining  latent  in  a  healed  lesion  of  that 
disease.^  According  to  Bosquenet  -  the  spirochetes  are 
commonly  found  in  gumma,  where  they  may  apparently 
remain  latent  for  a  long  time.  The  fact  that  gumma  have 
not  been  considered  infectious  has  been  urged  as  an^argu- 
ment  against  the  pathogenicity  of  the  spirochetes.  It  is 
now,  however,  generally  thought  that  the  spirochetes  in 
these  tumors  are  infective. 

Relapsing  Fever.  —  There  are  several  types  of  relapsing 
fever  having  more  or  less  well  marked  geographical  limita- 
tions. The  disease  is  characterized  by  well  defined  febrile 
"  relapses "  with  equally  well  defined  afebrile  intervals. 
The  different  forms  of  the  disease  are  caused  by  slightly  dif- 
fering species  of  spirochetes,  and,  as  will  be  referred  to  in  the 
last  chapter,  these  parasites  are  undoubtedly  transmitted 
by  insect  carriers.  According  to  Craig,^  it  has  been  demon- 
strated by  Brcinl  and  Kinghorn  and  by  Dutton  and  Todd 
that  though  Spirocheta  duttoni  is  not  found  in  the  blood 
during  the  afebrile  period,  the  blood  nevertheless  is  infec- 
tious. Mackie  has  shown  the  same  for  S.  carteri,  and 
Darling  *  has  shown  that  the  blood  from  the  afebrile  stage 
and  from  entirely  recovered  animals  is  still  infectious. 
Darling's  work  was  done  in  Panama. 

1  Pasini,  cited  by  RoHcnbergor,  New  York  M.  J.  [etc.],  1908, 
LXXXVII,  394. 

"^  Bosquenet,  Spirochactes,  Phila.,  1911,  .51. 

'  (^raiK,  1'lie  M:il:iri:il  Fevers,  New  York,  1909,  447. 

*  Darling,  Arch.  Int.  Med.,  Cliicago,  1909,  150. 


CARRIERS  AND  MISSED  CASES  117 

Vincent's  Angina.  —  It  seems  highly  probable  that  this 
disease  is  caused  by  the  spirochetes  which  are  found  con- 
stantly in  the  lesions.  That  many  mild  missed  cases,  and 
perhaps  true  carriers  occur  is  probable.  Farley/  in  report- 
ing an  institutional  outbreak  of  this  disease,  says  that  a 
number  of  children  were  found  without  any  constitutional 
symptoms,  but  with  a  slight  exudation  on  the  tonsils  or  with 
spongy  gums,  and  that  in  these  the  spirochetes  were  found 
to  be  present.  These  cases  were  not  discovered  until  a 
systematic  examination  was  made  of  all  the  children  and 
the  outbreak  ceased  on  their  removal  from  the  institution. 
Kerr  ^  reports  an  outbreak  in  the  Linden  Lodge  School  in 
London,  consisting  of  about  20  cases,  and  due  apparently 
to  unnoticed  chronic  and  subacute  cases  which  attracted 
no  attention  until  they  were  sought  for. 

Yellow  Fever.  —  The  parasite  which  is  the  cause  of  yellow 
fever  is  still  unknown,  although  fortunately  for  preventive 
medicine  we  have  ver}^  accurate  knowledge  of  the  manner  in 
which  the  disease  is  transmitted.  As  in  scarlet  fever,  so  in 
yellow  fever  lack  of  knowledge  of  the  parasite  renders  diffi- 
cult the  recognition  of  carrier  cases  if  they  exist.  But  there 
is  abundant  clinical  evidence  that  many  very  mild  and  at^^p- 
ical  cases  occur  which  it  is  impossible  to  recognize.  It  is  in 
young  children  chiefly  that  this  slight  disturbance  is  pro- 
duced by  the  infection.  A  similar  phenomenon  is  noted  in 
malarial  disease,  and  young  children  are  the  chief  source  of 
infection  in  both  j^ellow  fever  and  malaria.  The  fact  of  the 
mildness  of  these  cases,  their  frequency,  and  the  impossibility 
of  making  a  diagnosis,  has  been  insisted  upon  by  Finlay, 
Gorgas,  Guiteras,  Carter,  Agramonte,  Marchoux  and  others. 
Even  in  adults,  walking  cases,  which  it  is  impossible  to  dis- 
cover by  an  ordinary  examination,  are  not  rare.  Thus  itwas 
claimed  that  during  an  outbreak  in  Louisiana  a  single  walk- 
ing case  carried  the  disease  to  three  different  communities. 

1  Farley,  J.  Am.  M.  Ass.,  Chicago,  1910,  LIV,  1516. 

2  Rep.  Med.  Off.  of  Education,  Lond.,  1909,  63. 


118       THE  SOURCES  AND  MODES  OF  INFECTION 

Amebic  Dysentery.  —  A  number  of  observers  have  re- 
ported finding  Entameha  histolytica,  which  is  the  cause  of 
this  disease,  in  the  intestines  of  healthy  persons.  It  is 
now  beheved  that  most  of  these  reports  are  based  on  error 
due  to  confusing  the  pathogenic  species  named  above  with 
harmless  saprophytes.  This  is  the  view  of  Vedder  ^  iand 
Craig.2  Although  the  laboratory  evidence  of  the  existence 
of  carriers  of  dysentery  amebse  is  uncertain  or  lacking,  there 
is  epidemiological  evidence  that  these  parasites  are  some- 
times found  in  persons  for  a  long  time  after  recovery,  and 
may  also  be  found  in  the  feces  before  the  disease  develops. 
Martini  ^  reports  a  case  in  which  the  sickness  lasted  from 
the  15th  of  September  to  the  1st  of  December,  1907,  but  in 
which  the  amebse  persisted  until  the  last  of  January,  1908. 
Vincent  ^  reports  several  instances  in  which  persons  were 
carriers  for  five  months  after  their  return  to  France  from 
Tonkin.  Lemoine  ^  had  under  observation  a  man  who  con- 
tracted the  disease  in  China  in  1897  and  returned  to  France 
and  transmitted  the  disease  to  another  in  1908.  Cameron  ® 
reports  a  soldier  returned  to  Scotland  from  the  Boer  War, 
and  apparently  well  for  6  years,  but  who  then  developed  a 
liver  abscess  in  which  amebse  were  found. 

Poliomyelitis.  ■ —  The  disease  known  as  acute  anterior 
poliomyelitis,  or  infantile  paralysis,  has  been,  during  the 
past  fifteen  years,  occurring  with  increasing  frequency. 
It  usually  appears  in  well-defined  local  outbreaks  lasting 
from  a  few  weeks  to  a  few  months.  Except  in  the  largest 
cities  the  outbreaks  are  not  often  of  long  duration.  "  Spo- 
radic "  or  somewhat  isolated  cases  also  doubtless  occur, 

'  Vedder,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVI,  870. 

2  Craig,  J.  Infect.  Dis.,  Chicago,  1908,  V,  324;  The  Parasitic 
Amoeba)  of  Man,  Phila.,  1911. 

»  Martini,  Arch.  f.  S(;liiffs-  u.  Tropen-ITyg.,  Cassel,  1908,  XII,  588. 

*  Vincent,  Bull.  Soc.  path,  exot..  Par.,  1909,  II,  78. 

^  Lemoine,  Bull,  ct  m6m.  Soc.  m6d.  d.  h6p.  do  Par.,  1908,  3d  Ser., 
XXV,  640. 

8  Cameron,  Brit.  M.  J.,  Lond.,  1911,  I,  973. 


CARRIERS  AND  MISSED  CASES  119 

though  it  is  not  unlikely  that  some  which  are  reported  under 
this  name  may  be  due  to  a  totally  different  cause  from  that 
which  gives  rise  to  the  "  epidemic  "  form,  just  as  cases  of 
cerebro-spinal  meningitis,  closely  resembling  the  disease 
caused  by  the  Weichselbaum  diplococcus,  may  be  produced 
by  several  other  infective  agents.  For  many  years  epi- 
demiologists have  considered  poliomyelitis  as  an  infectious 
and  contagious  disease,  though  many  have  thought  the 
evidence  of  communicability  not  to  be  entirely  satisfac- 
tory. In  fact,  the  epidemiological  evidence  of  the  conta- 
giousness of  this  disease,  and  of  cerebro-spinal  meningitis, 
is  almost  on  a  par.  The  contagiousness  of  both  diseases 
is  certainly  not  very  marked;  that  is,  the  chance  of  a  frank 
case  giving  rise  to  another  frank  case,  either  in  homes  or  in 
institutions,  is  very  small.  When  an  apparently  contagious 
disease,  yet  one  only  slightly  so,  appears  in  well-marked 
outbreaks,  it  is  pretty  safe  to  assume  the  existence  of  large 
numbers  of  carriers  or  of  mild  atypical  and  unrecognized 
cases.  The  epidemiology  of  cerebro-spinal  meningitis  was 
inexplicable  until  the  carriers  of  that  disease  were  discov- 
ered. The  explanation  of  its  spread  now  involves  no  more 
difficulties  than  does  that  of  scarlet  fever  or  diphtheria. 
The  epidemiological,  and  indeed  clinical  resemblance  of 
cerebro-spinal  meningitis  and  poliomyelitis  led  some,  even 
before  the  work  of  Flexner  and  Clark,  and  Lucas  and 
Osgood,  to  suspect  the  existence  of  carriers.  The  exist- 
ence of  numerous  "  abortive  "  cases,  as  they  have  been 
called,  had  long  been  considered  probable. 

Laboratory  Studies.  —  To  determine  definitely  the  ex- 
istence of  either  carriers  or  atypical  cases  of  any  infectious 
disease  by  means  of  epidemiological  studies  is  extremely 
difficult,  and  to  determine  their  number  is  entirely  impos- 
sible. Fortunately  experimental  laboratory  work,  culmi- 
nating in  the  investigations  of  Flexner  and  Lewis,^  have 

1  Flexner  and  Lewis,  J.  Am.  Med.  Ass.,  Chicago,  1909,  LIII,  1639, 
1913. 


120       THE  SOURCES  AND  MODES  OF  INFECTION 

shown,  by  repeated  transfers  of  the  virus  through  monkeys, 
that  poHomyehtis  is  in  all  probability  due  to  a  living  con- 
tagium.  Subsequent  studies  have  shown  that  the  virus  is 
filterable;  that  it  is  found  in  various  fluids  and  organs  of 
monkeys  including  the  nasal  and  pharyngeal  mucous  mem- 
brane, and  presumably  also  in  the  mucus ;  and  that  animals 
may  be  infected  not  only  by  injection  into  the  central 
nervous  system,  but  also  by  injection  into  the  subcuta- 
neous tissue,  and  by  application  of  the  virus'  to  the  scari- 
fied and  healthy  mucous  surfaces.  The  spinal  fluid  very 
early  shows  quite  characteristic  changes,  and  "  immunity 
principles  "  (capable  of  neutralizing  the  virus  in  the  test 
tube)  are  found  in  the  blood  of  animals,  and  human  beings 
who  have  had  the  disease.^ 

Poliomyelitis  Carriers.  —  By  means  of  the  experimental 
methods  rendered  possible  by  this  work,  it  has  been  shown 
that  in  monkeys,  at  least,  the  virus  of  this  disease  remains 
in  the  nose  and  throat  after  the  clinical  symptoms  have 
subsided.  Thus  Osgood  and  Lucas  -  found  the  virus  in 
the  naso-pharyngeal  mucous  membrane  of  two  monkeys 
6  weeks  and  5^  months  respectively  after  the  acute  symp- 
toms of  the  disease  had  disappeared,  and  Flexner  and 
Clark  found  the  virulence  to  persist  4  weeks  in  a  monkey 
studied  by  them.  Tluis  the  existence  of  chronic  conva- 
lescent carriers  in  inoculated  monkeys  is  definitely  proved. 
As  the  virus  has  been  shown  by  Flexner  and  Clark  '  to 
exist  in  the  tonsillar  tissues  of  human  beings  during  the  dis- 
ease, just  as  it  is  found  in  the  mucous  mcunbraue  of  monkeys, 
it  seems  reasonable  to  expect  that  it  only  needs  further 
investigation  to  demonstrate  the  existence  of  human  car- 
riers of  this  disease.  Occasionally  observers  have,  for  epi- 
demiological reasons,  suspected  certain  persons  of  being 

'  Flexner  and  Lewis,  J.  Am.  Med.  Ass.,  Chicago,  1910,  LIV, 
1780. 

2  Osgood  and  Liinas,  J.  Am.  Med.  Ass.,  Chicago,  1911,  LV,  495. 
*  Flexner  and  Clark,  .J.  Am.  Med.  A.ss..  ('hicago,  1911,  1085. 


CARRIERS  AND  MISSED  CASES  121 

carriers.  Thus  Lovett  ^  states  that  he  has  a  number  of 
such  cases  in  his  records,  and  in  11  instances  the  disease 
followed  intimate  contact  with  persons  who  had  previously 
suffered  from  it.  Such  cases  have  also  been  reported  by 
Krause.^  Anderson  ^  in  Nebraska  notes  a  number  of  in- 
stances in  which  the  disease  seems  to  have  been  carried  by 
well  persons.  Thus  a  girl  who  had  visited  in  Stromberg, 
where  the  disease  prevailed,  returned  to  a  farm  many 
miles  distant  and  a  few  days  later  a  case  of  poliomyelitis 
developed,  followed  by  others  on  that  and  a  near-by  farm. 
In  another  instance  a  thresher  apparently  carried  it  from 
his  own  family  to  the  place  where  he  worked.  In  two  other 
instances  peddlers  seemed  to  be  carriers.  Similar  observa- 
tions have,  in  England,  been  made  by  Reece  and  Farrar.* 

Poliomyelitis :  Atypical  Cases.  —  Ever  since  Wickman's 
studies  in  Sweden  it  has  been  believed  that  so-called  "  abor- 
tive "  cases  of  this  disease  are  quite  common.  These  cases 
may  show  some  slight  symptoms  referable  to  the  nervous 
system,  such  as  headache,  pain,  tenderness  and  rigidity  of 
neck,  hypersthesia  and  neuralgic  pains;  and  some  think 
that  tonsillitis  and  gastro-intestinal  irritation  without  ner- 
vous symptoms  may  be  due  to  the  same  pathogenic  agent. 
According  to  Frost, ^  Wickman  found  such  abortive  cases 
to  equal  in  number  15  per  cent  of  the  frank  cases.  In 
Massachusetts  in  1909  there  were  49  possibly  abortive 
cases  observed  in  connection  with  150  acknowledged  cases. 
Frost  himself  in  an  outbreak  in  Hancock  County,  la., 
found  25  abortive  cases  and  5  frank  cases.  That  some  at 
least,  and  perhaps  a  large  proportion,  of  these  abortive 
cases  are  really  poliomyelitis,  is  shown  by  the  finding  of 

1  Lovett,  Rep.  State  Bd.  of  Health,  Mass.,  1909. 
^  Krause,  Therapie  der  Gegenwart,  1911,  LII,  145, 
'  Anderson,  Pediatrics,  N.  Y.  &  Lond.,  1910,  XXII,  543. 
*  Reece  and  Farrar,  Rep.  to  Local  Gov.  Bd.  Lond.,  1912,  No.  61. 
5  Frost,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Pub.  Health  Bull. 
No.  44,  1911. 


122       THE  SOURCES  AND  MODES  OF  INFECTION 

"  immunizing  principles  "  in  their  blood.  Anderson  and 
Frost  ^  state  that  Netter  and  Levaditi  demonstrated  a 
case  in  this  way,  and  the  authors  themselves  showed  the 
presence  of  "  immunizing  principles  "  in  the  blood  of  6  of 
9  suspected  abortive  cases. 

In  view  of  the  epidemiological  facts,  and  the  experi- 
mental data,  it  seems  not  unsafe  to  surmise  that,  with  the 
perfection  and  extended  application  of  laboratory  methods 
of  diagnosis,  carriers  and  mild  atypical  cases  of  poliomye- 
litis will  be  shown  to  be  common,  and  it  is  not  unlikely  that 
they  may  prove,  as  in  cerebro-spinal  meningitis,  many  times 
more  numerous  than  are  frank  cases  of  the  disease. 

Latency  a  Common  Phenomenon.  —  The  laity  and  not  a 
few  physicians  are  still  incredulous  that  there  can  be  diph- 
theria infection  unless  the  patient  is  sick  in  bed  and  the 
throat  choked  with  exudation,  or  that  there  can  be  scarlet 
fever  without  high  fever  and  an  extensive  eruption.  Still 
less  are  they  willing  to  admit  that  perfectly  well  persons 
can  carry  and  reproduce  in  their  bodies  the  virus  of  the 
infectious  diseases.  It  is  difficult  for  many  to  realize  that 
the  virus  of  disease  may  remain  latent  in  the  body,  for 
long  periods,  without  causing  symptoms.  The  facts  pre- 
sented in  the  preceding  pages  have  been  gathered  to  show 
that  latency  is  a  common  phenomenon,  and  for  this  pur- 
pose, besides  many  common  human  infections,  a  number  of 
diseases  have  been  referred  to,  not  transmissible  to  human 
beings  and  of  little  interest  to  health  officials,  but  which 
seem  to  illustrate  this  phenomenon.  Infection  without 
symptoms  is  no  cause  for  surprise,  but  may  be  expected  in 
any  parasitic  disease.  There  may  be  exceptions,  as  is  said 
to  be  the  case  in  relapsing  fever  and  African  East  Coast 
cattle  fever  (caused  by  Th.  parva).  But  these  exceptions, 
rather  than  the  existence  of  latency  and  atypical  types, 
should  be  cause  for  surprise. 

»  FroHt,  J.  Am.  Med.  Ass.,  Chicago,  1911,  LVI,  663. 


CARRIERS  AND  MISSED  CASES  123 

Laboratory  Evidence  of  Carriers.  —  Definite  knowledge 
as  to  the  existence  and  number  of  carriers  must  rest  almost 
entirely  upon  evidence  furnished  by  the  finding  in  the  body 
of  the  causative  agents  of  disease,  bacteria  or  protozoa,  or 
the  demonstration  in  the  blood  or  tissues  of  an  unknown 
infective  principle,  as  in  the  case  of  poliomyelitis.  Actu- 
ally, almost  all  such  evidence  depends  upon  the  finding  of 
disease-producing  bacteria  or  protozoa  in  the  bodies  of 
healthy  persons  or  animals.  Those  persons  who  do  not 
believe  that  the  causative  relation  between  these  minute 
forms  of  life  and  disease  has  been  established  with  a  rea- 
sonable degree  of  certainty  will  of  course  attach  little  weight 
to  the  bacteriological  evidence  of  the  existence  of  carriers. 
With  such  I  cannot  agree.  On  the  contrary,  the  causation 
of  certain  diseases  by  bacteria  seems  to  me  to  be  one  of  the 
best-established  truths  of  medical  science,  and  it  is  conse- 
quently entirely  legitimate  to  make  use  of  bacteriological 
evidence  in  developing  the  theory  and  practice  of  preven- 
tive medicine.  Many,  while  admitting  that  we  have  satis- 
factory evidence  that  some  diseases  are  caused  by  specific 
bacteria  or  protozoa,  are  unwilling  to  admit  that  the  evi- 
dence is  conclusive  as  to  the  causative  relation  of  certain 
other  alleged  pathogens  and  the  diseases  said  to  be  due  to 
them.  Indeed,  almost  everyone  takes  this  attitude  towards 
some  disease.  It  happiens,  however,  that  in  the  opinion  of 
the  majority  of  the  most  competent  observers  the  evidence 
is  especially  strong  as  regards  the  causative  agent  of  chol- 
era, typhoid  fever,  diphtheria,  cerebro-spinal  meningitis, 
sleeping  sickness  and  malaria.  And  it  is  particularly  for 
these  diseases  that  we  have  abundant  evidence  as  regards 
the  numbers  and  importance  of  carriers. 

Laboratory  Evidence  of  Atypical  Cases.  —  While  acute 
clinical  observers  have  at  all  times  recognized  many  atypical 
cases  which  would  have  been  overlooked  by  the  average 
man,  it  was  from  the  nature  of  things  impossible  to  know 
how  far  or  how  often  a  disease  could  deviate  from  the  nor- 


124       THE  SOURCES  AND  MODES  OF  INFECTION 

mal  when  the  only  criterion  for  the  determination  of  the 
disease  was  the  symptom  complex  of  the  normal  type.  It 
is  only  the  discovery  of  the  germ,  and  the  ability  to  recog- 
nize it,  which  enables  us  to  take  a  wider  view  of  an  infec- 
tious disease,  and  to  see  that  it  includes  far  more  types  and 
cases  than  was  at  first  suspected.  It  is  only  the  work  of 
the  laboratory  that  makes  it  possible  to  recognize  the  mild 
atypical  cases  of  diphtheria,  typhoid  fever  and  malaria. 
The  clinicians  have  been  willing  to  accept,  though,  it  must 
be  confessed,  with  a  little  hesitancy,  the  teachings  of  the 
laboratory  men  in  regard  to  prevalence  of  atypical  cases. 
Some  are  even  emboldened  to  proceed  along  lines  where 
the  laboratory  men  cannot  as  yet  go,  and  to  recognize 
atypical  scarlet  fever  which  they  would  formerly  have 
passed  by,  and  to  postulate  the  "  abortive  "  type  of  polio- 
myelitis. Yet  when  the  laboratory  man  points  out  the 
true  carrier  and  suggests  danger  from  him  as  well  as  from 
the  atypical  case,  many  a  clinician,  and  not  a  few  epidemi- 
ologists as  well,  hesitate  to  follow. 

Carriers  Vary  in  Numbers.  —  One  of  the  important  facts 
noticeable  in  the  study  of  this  subject  is  the  great  varia- 
tion in  the  number  of  carriers  in  different  diseases.  It 
ought  to  be  determined  by  a  sufficient  number  of  observa- 
tions j  ust  how  many  carriers  there  are  in  different  diseases 
among  the  general  public  and  among  contacts  at  different 
ages,  at  different  seasons,  and  in  different  places.  Un- 
fortunately the  observations  have  not  as  yet  been  exten- 
sive enough  to  warrant  any  definite  conclusions,  though 
some  quite  striking  differences  are  apparent.  Probably  the 
number  of  carriers  is  on  the  whole  greater  in  pneumonia 
than  in  any  other  disease,  including  at  times  half  the  total 
population.  In  certain  protozoan  diseases  the  percentage 
of  carriers  may  ])e  even  higher  within  limited  groups,  as 
among  children  in  intensely  malarious  districts.  So,  too, 
carriers  of  the  trypanosomes  of  sleeping  sickness  are  at 
times  very  numerous.     In  the  case  of  animal  diseases,  as 


CARRIERS  AND  MISSED  CASES  125 

Texas  cattle  fever,  the  proportion  of  infected  animals  is 
very  large.  Among  human  diseases  it  would  appear  that 
influenza  carriers  are  very  numerous,  though  the  identity 
of  the  causative  agent  has  not  been  so  well  determined,  and 
the  number  of  observations  is  not  as  large  as  for  many  other 
diseases.  It  is  certain  that  cerebro-spinal  meningitis  car- 
riers are  many  times  more  numerous  than  the  cases — in  the 
opinion  of  many,  from  ten  times  to  twenty  times  as  numer- 
ous. Under  ordinary  conditions,  with  a  moderate  preva- 
lence of  the  disease,  diphtheria  carriers  equal  about  one  per 
cent  of  the  population,  and  during  outbreaks  the  percent- 
age, particularly  among  children,  is  many  times  as  great. 
Probably  typhoid  carriers  are  not  so  numerous  as  are 
diphtheria  carriers,  but  there  are  not  many  data  as  to  the 
numbers  among  either  the  general  public  or  among  con- 
tacts. In  neither  human  nor  rat  plague  do  carriers  appear 
to  be  either  numerous  or  important.  There  is  even  less 
evidence  of  the  existence  of  carriers,  certainly  of  chronic 
carriers,  of  smallpox;  and  for  measles  the  clinical  evidence 
that  there  are  no  carriers  is  very  strong. 

Relation  between  Number  of  Carriers  and  Infectivity.  — 
Here  again  data  are  too  few  to  warrant  more  than  a  sugges- 
tion, but  one  cannot  but  be  struck  by  the  fact  that  the  most 
infectious  diseases  show  the  fewest  carriers,  while  some  of 
the  diseases  which  are  only  slightly  contagious  show  very 
many  more  carriers  than  cases.  Thus  smallpox  and  mea- 
sles, considered  perhaps  the  most  contagious  of  diseases,  are 
not  certainly  known  to  give  rise  to  the  carrier  condition. 
Diphtheria  is  not  so  infectious  as  measles;  that  is,  a  case, 
brought  in  contact  with  susceptibles,  does  not  so  surely 
give  rise  to  other  cases;  and  carriers  of  diphtheria  are  quite 
numerous.  Cerebro-spinal  meningitis  exhibits  many  car- 
riers, and  its  ineffectivity,  as  measured  by  contagion  in  the 
family  and  institution,  is  small.  Pneumonia  has  the  most 
carriers  of  all  and  is  the  least  contagious. 


126   THE  SOURCES  AND  MODES  OF  INFECTION 

Virulence  of  Germs  in  Carriers.  —  The  question  of  the 
infecting  power  of  carriers  is  the  crucial  one  of  the  whole 
subject.  One  way  of  testing  this  is  by  testing  by  animal 
experiment  the  virulence  of  the  germs  which  the  carrier  is 
producing.  Unfortunately,  owing  to  insusceptibility  of  the 
lower  animals,  or  the  difficulties  of  the  technique,  or  the 
cost  of  susceptible  animals,  like  the  apes,  renders  numerous 
observations  out  of  the  question.  In  one  disease,  diphthe- 
ria, in  which  experimentation  is  comparatively  easy,  it  has 
been  shown  that  in  a  varying  percentage  of  carriers  the 
bacilli  are  virulent,  often  exceedingly  virulent,  though  there 
is  a  large  number  of  carriers  in  which  they  are  not  virulent. 
The  actual  number  of  carriers  of  virulent  germs  is  never- 
theless shown  to  be  very  large.  The  pneumococcus  found 
in  well  persons  is  virulent  for  rabbits,  though  less  so  than 
are  cocci  from  cases  of  pneumonia.  Tests  on  the  lower 
animals  for  the  virulence  of  typhoid  bacilli  are  of  little 
value,  but  it  is  worthy  of  note  that  a  case  of  typhoid  fever 
in  a  human  being  has  recently  resulted  from  drawing  into 
the  mouth  a  culture  of  a  typhoid  bacillus  derived  from  a 
carrier. 

In  some  of  the  diseases  of  the  lower  animals  direct  experi- 
ment has  demonstrated  the  virulence  of  disease  germs  from 
healthy  individuals.  This  has  been  abundantly  proved  in 
Texas  cattle  fever  and  in  certain  trypanosome  infections. 

Carriers  as  a  Source  of  Protozoan  Disease.  —  There 
seems  to  be  little  disposition  in  any  quarter  to  question  the 
importance  of  carriers  of  the  malarial  Plasmodium  in  the 
extension  of  malarial  disease.  Yet  so  far  as  I  know  there 
arc  no  experiments  which  demonstrate  such  transmission, 
and  few  if  any  clinical  observations  which  would  indicate 
such  transmission.  It  is  simply  assumed  that  the  numer- 
ous well  persons  carrying  Plasmodium  must  be  a  source 
from  which  oftentimes  the  mosquitoes  get  the  infection 
which  they  transmit  to  others.  Probably  the  reason  why 
this  view  is  so  readily  accepted  without  any  demand  for 


CARRIERS  AND  MISSED  CASES  127 

rigid  experimental  or  epidemiological  proof  is  that  the  mode 
of  transmission  of  this  disease  is  established  on  such  con- 
vincing evidence.  It  seems  certain  that  it  is  only  trans- 
mitted by  mosquitoes,  and  that  mosquitoes  obtain  the 
parasites  only  by  previously  biting  infected  human  beings. 
So,  too,  because  the  mode  of  transmission  of  sleeping  sick- 
ness is  definitely  determined,  no  one  looks  for  the  origin  of 
this  disease  outside  the  bodies  of  living  beings,  and  as  many 
human  beings  are  shown  to  be  "  carriers  "  of  the  trypano- 
some,  such  persons  are  believed  to  be  a  principal  source  of 
the  disease. 

Carriers  as  a  Cause  of  Bacterial  Diseases.  —  In  at  least 
one  bacterial  disease,  namely  "  white  diarrhea  of  chicks," 
due  to  B.  pullorum,  it  has  been  definitely  shown  that  adult 
carrier  hens  infect  their  eggs  and  are  thus  the  principal 
factor  in  the  spread  of  the  disease.  In  no  other  animal 
disease  due  to  bacteria  does  the  carrier  question  appear  to 
have  been  so  well  worked  out. 

While  the  existence  of  numerous  carriers  has  been  amply 
demonstrated  in  such  diseases  as  cholera,  typhoid  fever, 
dysentery,  diphtheria  and  cerebro-spinal  meningitis,  their 
importance  in  the  spread  of  these  and  similar  diseases  has 
been  questioned  by  many  who  never  question  the  impor- 
tance of  carriers  in  the  spread  of  malarial  disease.  The 
reason  for  this,  doubtless,  is  that  the  mode  of  transmission 
of  these  diseases  is  not  so  well  understood  because  they  do 
not  readily  permit  the  use  of  experimental  methods.  Every- 
one feels  sure  how  every  case  of  malaria  is  caused.  On  the 
other  hand,  we  are  often,  perhaps  usually,  in  doubt  in  cases 
of  typhoid  fever,  cholera  and  diphtheria  as  to  the  mode  of 
transmission  of  the  infection  and  the  source  from  which  it 
comes.  When  there  are  many  possible  sources  and  modes 
of  infection  it  is  not  easy  to  determine  the  right  one. 

Evidence  of  Contagion  the  Same  as  for  Cases.  —  It  is 
fair  to  claim  that  the  evidence  of  the  infectivity  of  carriers 
is  the  same  as  the  evidence  of  the  infectivity  of  cases.     We 


128        THE  SOURCES  AND  MODES  OF  INFECTION 

believe  that  frank  cases  of  diphtheria  are  contagious  be- 
cause it  very  generally  happens  that  persons  exposed  to 
them  develop  the  disease,  and,  conversely,  because  a  certain 
proportion  of  the  recognized  cases  have  been  in  relation  to 
other  cases.  We  believe  that  typhoid  fever  is  contagious 
because  a  certain  number  of  persons  exposed  to  cases  of 
the  disease  contract  it,  even  though  the  proportion  is 
smaller  than  in  diphtheria.  It  is  considered  a  further 
proof  that  many  cases  of  typhoid  can  be  shown  to  have 
had  some  connection  with  previous  cases.  When  a  con- 
siderable number  of  cases  of  typhoid  fever  are  caused  by 
the  consumption  of  milk,  and  the  milk  is  known  to  have 
been  handled  by  a  typhoid  patient,  or  even  to  have  come 
from  premises  occupied  by  such  a  patient,  it  is  generally 
assumed  that  the  contagion  was  derived  from  the  patient. 

In  precisely  the  same  way  it  has  been  shown  in  the  pre- 
ceding pages,  and  much  more  additional  proof  of  the  same 
kind  is  obtainable,  that  persons  in  contact  with  diphtheria 
carriers,  and  indeed  the  carriers  themselves,  not  rarely 
develop  the  disease.  It  has  also  been  shown  that  persons 
with  diphtheria  have  often  been  in  relation  to  carriers. 
The  number,  it  is  true,  is  not  very  great,  and  it  cannot  be 
so  great  as  for  cases;  for  while  it  is  comparatively  easy  to 
recognize  any  frank  case  in  the  environment  of  any  given 
patient,  it  is  not  possible  to  recognize  any  carrier  there 
may  be,  except  by  cultures  from  every  one  with  whom  the 
patient  has  come  in  contact. 

In  typhoid  fever  it  is  easier  to  find  carriers  because  ty- 
phoid fever,  more  than  any  other  disease,  is  spread  through 
milk,  water  or  food;  and  outbreaks  so  caused  are  often 
traced  to  some  definite  locality,  often  to  a  single  house,  so 
that  the  search  for  carriers  becomes  easier.  Hence  we 
have  more  definite  proof  that  typhoid  fever  is  caused  by 
carriers  than  we  have  that  any  other  human  bacterial  dis- 
ease is  so  caused.  The  outbreaks  of  typhoid  fever  which 
have  been  shown  to  have  a  definite  relation  to  carriers 


CARRIERS  AND   MISSED  CASES  129 

afford  as  good  evidence  that  carriers  are  the  cause  of  this 
disease  as  there  is  that  cases  give  rise  to  other  cases. 

Lack  of  Statistical  Evidence  Alleged.  —  Hamer  ^  has 
prged  that  the  mere  association  of  a  carrier  and  a  case  is  no 
proof  of  a  causative  relation,  and  he  says  that  the  finding 
of  carriers  in  connection  with  certain  outbreaks  of  typhoid 
fever  is  of  little  importance  unless  we  have  some  idea  of 
the  number  of  carriers  in  the  general  population.  He  does 
well  to  call  attention  to  the  lack  of  satisfactory  data,  but 
when  only  1  carrier  is  found  among  250  persons  and  3 
among  nearly  1000,  it  is  fair  to  assume  that  carriers  are  not 
very  common. 

Carriers  Often  Appear  not  Dangerous.  —  It  is  certainly  a 
fact  that  carriers  often  appear  to  be  non-infectious.  Many 
carriers  of  typhoid  bacilli  and  of  diphtheria  bacilli  have 
been  known  to  remain  such  for  long  periods  of  time  with- 
out apparently  infecting  members  of  their  families  or  others 
brought  in  close  contact  with  them.  As  shown  on  page  84, 
diphtheria  carriers  have  been  followed  in  schools  in  Boston 
and  Providence  and  no  infection  from  them  has  been  dis- 
covered. Diphtheria  carriers  have  been  discharged  from 
hospitals  and  no  cases  have  developed  in  their  homes. 
These  and  similar  facts  certainly  demonstrate  that  all  car- 
riers do  not  at  all  times  cause  disease  in  those  with  whom 
they  are  brought  in  contact.  Why  this  is  so  may  be  due 
to  a  variety  of  causes.  Thus  the  excretion  of  bacteria  is  in 
many  cases  notoriously  intermittent.  There  is  also  good 
reason  for  believing  that  the  bacteria  have  in  many  cases 
lost  their  virulence.  Perhaps  sometimes  they  are  produced 
in  relatively  small  numbers.  Again,  many  of  the  persons 
exposed  are  doubtless  immune.  Furthermore,  we  must  bear 
in  mind,  as  will  be  referred  to  in  the  following  chapter,  that 
the  infecting  power  of  even  frank  cases  of  disease  is  very 
much  less  than  has  generally  been  supposed.  Such  cases 
may  often  remain  in  close  association  with  susceptible  per- 

^  Hamer,  Proc.  Roy.  Soc,  Med.,  1911,  IV,  Epidemiol.  Sect.,  105. 


130       THE  SOURCES  AND  MODES  OF  INFECTION 

sons  without  the  conditions  being  present  for  a  transfer 
of  an  effective  amount  of  infective  material.  One  would 
expect  this  to  happen  still  more  often  with  carriers. 

On  the  other  hand,  there  is  much  evidence  which  shows 
that  carriers  at  times  do  cause  disease.  To  most  persons 
the  evidence  of  this  is  conclusive.  The  question  at  issue 
merely  is,  How  often  does  this  occur?  To  what  extent  are 
carriers  a  factor  in  the  maintenance  of  the  infectious  dis- 
eases? To  the  writer  it  appears  that  many  things  strongly 
point  to  carriers  as  a  factor  of  great  moment.  The  prob- 
ability of  this  is,  I  believe,  sufficient  to  warrant  our  modi- 
fying our  restrictive  measures  accordingly.  I  nevertheless 
freely  admit  that  we  are  greatly  in  need  of  more  statistical 
evidence. 

There  are  still  many  problems  concerning  the  relation  of 
carriers  to  disease  which  need  further  careful  study,  and  it 
is  not  for  a  moment  claimed  that  the  "  carrier  theory,"  so 
called,  satisfactorily  explains  every  epidemiological  phe- 
nomenon. There  are  many  which  it  does  not  explain  at 
all.  On  the  other  hand,  some  of  the  most  important  phe- 
nomena of  the  extension  of  the  contagious  diseases  are  far 
better  explained  by  the  newly  discovered  facts  concerning 
carriers  than  by  any  of  the  theories  of  former  years.  We 
still  have  much  to  learn,  but  we  are  not  on  that  account 
justified  in  neglecting  the  facts  which  have  already  been 
learned  and  in  basing  our  practice  on  disproved  theories 
of  the  sources  of  infection. 

No  Sharp  Separation  between  Varieties  of  Carriers.  — 
'^riiat  typical  cases  of  disease  are  th(;  source  of  similar  cases 
follows  necessarily  from  the  very  definition  of  contagious- 
ness. That  mild  cases,  even  very  mild  and  atypical  cases, 
may  give  rise  to  typical  as  well  as  to  other  mild  cases  is 
recognized  by  everyone.  Both  clinicians  and  epidemiolo- 
gists have  always  believed  that  perfectly  well  persons  may 
be  the  bearers  of  infection  from  the  sick  to  others.  It 
was  believed  by  most,  and  is  now  by  many,  that  such  per- 


CARRIERS  AND  MISSED  CASES  131 

sons  carry  the  infection  in  the  hair  or  clothing  or  on  the 
hands.  The  discovery  that  the  germs  of  disease  may  grow 
in  the  body  without  causing  symptoms  has  forced  most 
rational  persons  to  the  belief  that  when  well  persons  carry 
infection  it  is  because  they  are  "  carriers,"  that  is,  are 
growers,  of  germs. 

It  is  probably  true  that  all  carriers  are  not  dangerous, 
certainly  not  at  all  times,  even  when  they  are  excreting 
bacilli.  We  know  that  in  some  diphtheria  carriers  the 
bacilli  are  not  virulent  for  test  animals  and  probably  not 
for  human  beings.  Certain  observers  of  high  standing  kave 
assumed  that  it  is  only  the  convalescent  carriers  and  the 
carriers  who  are  in  immediate  contact  with  the  sick  who 
are  dangerous;  that  is,  it  is  these  only  who  carry  virulent 
germs.  If  these  can  be  controlled  the  carrier  problem  is 
solved,  they  think.  I  am  willing  to  admit  that  the  severe 
case  is  potentially  more  dangerous  than  the  mild  case, 
that  the  mild  case  may  be  more  dangerous  than  the  car- 
rier, and  that  the  convalescent  carrier  may  be  more  dan- 
gerous than  the  chance  carrier  found  among  the  public  at 
large.  There  is  some  evidence  of  this,  and  it  is  not  im- 
probable that  bacteria  may  tend  to  lose  their  virulence  in 
passing  through  a  succession  of  immune  persons  (as  it  is 
not  improbable  that  they  may  increase  in  virulence  by 
passing  through  susceptible  persons);  but  I  can  see  no 
ground  at  present  for  the  assumption  that  virulent  bacilli 
derived  from  a  sick  person  may  be  carried  by  one  well  person 
but  that  when  they  pass  to  another  well  person  they  cease  to 
be  dangerous.  There  seems  to  be  no  ground  for  assuming 
that  a  virulent  germ  cannot  pass  from  carrier  to  carrier. 

Conclusions.  —  We  are  justified  from  the  evidence  pre- 
sented in  coming  to  the  following  conclusions: 

1.  Mild  atypical  and  unrecognized  cases  of  the  infectious 
diseases  are  often  extremely  common.  In  many  diseases 
they  may  be  more  numerous  than  the  recognized  cases. 

2.  Disease-producing  micro-organisms,  whether  bacteria 


132       THE  SOURCES  AND  MODES  OF  INFECTION 

or  protozoa,  frequently  persist  in  the  body  without  causing 
symptoms. 

3.  Sometimes  the  germs  remain  only  a  few  weeks  or 
months  after  convalescence,  and  sometimes  they  may  persist 
for  years,  perhaps  for  life.  Sometimes  these  carriers  give 
no  history  of  ever  having  been  sick. 

4.  While  the  bacteria  found  in  carriers  are  sometimes 
lacking  in  virulence,  many  times  they  show  the  highest 
degree  of  virulence. 

5.  There  is  ample  epidemiological  evidence  that  healthy 
carriers  as  well  as  mild  unrecognized  cases  are  the  source  of 
well-marked  outbreaks. 

6.  The  number  of  carriers  varies  greatly  in  different  dis- 
eases. From  20  to  50  per  cent  of  the  population  are  carriers 
of  pneumococci.  It  seems  probable  that  the  influenza  bacil- 
lus is  as  widely  distributed.  During  outbreaks  of  cerebro- 
spinal meningitis  the  number  of  carriers  may  be  from  10  to 
30  times  as  numerous  as  the  number  of  cases.  Even  when 
diphtheria  is  not  prevalent  1  per  cent  of  the  population  may 
be  carrying  the  bacilli,  and  during  outbreaks  the  number 
may  be  several  times  greater.  Probably  25  per  cent  of  all 
typhoid  fever  cases  excrete  bacilli  for  some  weeks  after  con- 
valescence, and  it  is  estimated  that  from  1  in  500  to  1  in  250 
of  the  population  are  chronic  carriers.  What  little  evidence 
there  is  indicates  that  carriers  arc  as  numerous  in  dysentery 
and  cholera  as  they  are  in  typhoid  fever.  In  yellow  fever, 
sleeping  sickness,  and  particularly  in  malaria,  carriers  are 
very  numerous.  There  is  evidence  that  there  are  not  many 
carriers  of  measles  or  smallpox. 

7.  Any  scheme  of  prevention  wliich  fails  to  take  into  ac- 
count carriers  and  missed  cases  is  doomed  to  partial  and 
perhaps  complete  failure, 


CHAPTER  III. 

LIMITATIONS    TO    THE   VALUE    OF   ISOLATION. 

Number  of  Mild  Cases  and  Carriers.  —  In  the  first  chapter 
the  attempt  was  made  to  show  that  pathogenic  organisms  do 
not  usually  develop  outside  of  the  body.  Except  for  a  few 
diseases,  or  under  unusual  circumstances,  the  saprophytic 
existence  of  disease  germs  is  not  to  be  looked  for.  Such 
sources  of  infection  are  much  rarer  than  is  generally  assumed, 
and  for  most  diseases  may  be  entirely  neglected.  In  the 
second  chapter,  evidence  was  presented  that  certain  other 
sources  of  infection  are  very  much  more  numerous  than  is 
generally  believed,  and  it  is  here  contended  that  no  scheme 
of  sanitation  can  have  a  scientific  basis,  or  can  have  any 
possibility  of  success,  which  does  not  take  full  cognizance  of 
them. 

It  must  be  admitted  by  all  that  mild  atypical  cases  of  con- 
tagious diseases  are  very  numerous.  Every  one  who  has  had 
any  experience  with  the  last  epidemic  of  smallpox  in  the 
United  States  and  England  must  have  had  many  unpleasant 
reminders  of  this.  Health  officers'  reports  are  full  of  instances 
of  the  introduction  of  the  disease  into  a  community  by  per- 
sons unsuspected  by  any  one  of  having  the  disease,  and  who 
often  give  rise  to  a  whole  series  of  cases.  Similar  experiences 
with  scarlet  fever  are  often  reported.  The  most  critical  inves- 
tigation, such  as  that  of  our  surgeons  in  the  Spanish  War, 
indicates  that  mild  unrecognized  cases  of  typhoid  fever  fully 
equal,  if  they  do  not  exceed,  the  number  of  cases  which 
are  recognized  and  reported.  Even  with  every  facility  for 
diagnosis,  the  amount  of  sore  throat  due  to  the  diphtheria 
bacillus,  but  not  so  suspected,  is  fully  equal  to  the  amount 
of   recognized    diphtheria;   and  in   many  other   infectious 

133 


134       THE  SOURCES  AND  MODES  OF  INFECTION 

diseases  these   mild    cases  occur  with  varying   degrees  of 
frequency. 

Usually  not  Recognized.  —  The  extent  to  which  these  mild 
atypical  cases  escape  recognition  varies  with  the  disease,  the 
social  condition  of  the  people  affected,  the  intelligence  and 
conscientiousness  of  the  physician,  and  the  attitude  of  the 
health  officer.  That  the  majority  of  people  will  not  consult 
a  physician  unless  they  are  decidedly  sick,  is  certain.  That 
they  will  refrain  from  doing  so  if  they  expect  to  be  reported 
to  the  health  officer  and  to  be  placed  under  various  restric- 
tions, is  but  in  accord  with  human  nature.  A  slight  sore 
throat,  or  a  fleeting  rash,  little  suggestive  of  danger,  will  be 
lightly  passed  over,  no  physician  will  be  called  and  no  pre- 
cautions taken,  and  often  there  will  be  no  thought  of  danger 
to  others.  It  has  always  been  known  that  a  certain  number 
of  mild  cases,  difficult  to  recognize,  could  be  expected  in 
almost  all  infectious  diseases,  but  it  remained  for  the  labora- 
tory worker  to  show  how  numerous  they  are  in  such  diseases 
as  typhoid  fever,  diphtheria,  plague  and  malaria.  The  micro- 
scopic demonstration  of  the  frequency  with  which  clinically 
unrecognizable  attacks  of  the  above  named  and  other 
diseases  occur,  had  called  the  attention  of  clinicians  and  epi- 
demiologists to  their  probable  occurrence  in  such  other  dis- 
eases as  scarlet  fever,  smallpox,  and  yellow  fever,  the  specific 
organisms  of  which  have  not  as  yet  been  discovered.  So  that 
at  the  present  time  the  most  careful  epidemiologists,  clinicians 
and  laboratory  workers  begin  to  realize  that  very  large  num- 
bers of  mild  atypical  and  unrecognizable  cases  are  bound  to 
occur  in  most  infectious  diseases.  But  as  yet  few  text-books 
on  sanitation,  clinical  medicine,  or  even  on  bacteriology,  lay 
sufficient  emphasis  on  this  fact.  Nothing  is  more  common 
than  to  find  the  young  man  just  from  the  medical  school,  as 
well  as  the  old  practitioner,  quick  to  deny  the  presence  of 
scarlet  fever,  diphtheria,  or  typhoid  fever  because  the  symp- 
toms are  not  severe  enough  or  because  they  deviate  too 
much  from  the  text-book  description.    But  the  large  number 


I 


LIMITATIONS  TO   THE  VALUE  OF  ISOLATION     135 

of  the  mild  and  aberrant  cases,  which  usually  remain  "  missed 
cases,"  and  their  importance  in  the  extension  of  the  infectious 
diseases,  must  now  be  admitted. 

Carriers  Exceedingly  Numerous.  —  Still  more  numerous 
are  the  pure  carriers,  those  persons  in  whose  bodies  the 
pathogenic  bacteria  and  protozoa  develop  without  causing 
symptoms.  The  recognition  of  this  element  of  danger  is  due 
entirely  to  laboratory  investigation,  but,  strange  to  say,  most 
workers  on  bacteriology  lay  no  more  stress  on  this  epidemio- 
logical factor  than  do  the  writers  of  treatises  on  hygiene  or 
of  text-books  of  medicine.  In  the  preceding  chapter  sufficient 
evidence  was  presented  to  demonstrate  the  very  great  fre- 
quency with  which  these  carrier  cases  occur.  Their  exist- 
ence and  the  virulence  of  the  germs  which  they  carry  are 
now  established  facts.  Numerous  instances  were  given  where 
such  carriers  appeared  to  have  transmitted  the  disease  to 
others.  Indeed  it  is  almost  inconceivable  that  it  should  be 
otherwise.  It  is  hardl}^  possible  that  virulent  typhoid  bacilli 
or  diphtheria  bacilli  produced  in  large  numbers,  as  they  fre- 
quently are  in  carriers,  should  not  be  equally  as  dangerous  as 
those  which  develop  in  the  bodies  of  the  sick.  That  is,  they 
are  equally  dangerous  potentially;  actually  the  well  person 
moving  freely  about  may  be  more  dangerous  to  the  com- 
munity than  the  sick  person  who  is  confined  to  the  house. 

Approaching  the  subject  from  another  standpoint,  it  is 
interesting  to  see  how  the  discovery  of  these  missed  and  car- 
rier cases  has  explained  so  much  which  we  formerly  did  not 
understand. 

Effort  to  "  Stamp  Out  "  Disease.  —  Twenty-five  or  thirty, 
years  ago  we  heard  a  great  deal  about  "stamping  out"  the 
contagious  diseases.  That  was  the  era  of  the  building  of  hos- 
pitals for  these  diseases,  of  the  organization  of  the  sanitary 
service,  of  the  discovery  of  pathogenic  bacteria.  The  wonder- 
ful decrease  in  smallpox,  the  successful  fight  against  cholera, 
the  almost  total  disappearance  of  typhus  fever,  and  the  com- 
plete disappearance  of  plague,  only  foreshadowed,  it  was  said, 


136       THE  SOURCES  AND  MODES  OF  INFECTION 

the  extermination  of  typhoid  fever,  diphtheria,  scarlet  fever 
and  measles.  It  was  claimed  that  in  those  diseases  which 
are  exclusively  contagious,  if  every  case  can  be  isolated  until 
it  is  free  from  infection,  the  disease  will  be  exterminated.  It 
was  believed  that  if  people,  and  especially  physicians,  would 
take  only  a  little  more  care,  practically  all  cases  of  these 
diseases  could  be  recognized  and  isolated.  It  was  also  thought 
to  be  not  very  difficult  to  control  them  until  infection  had 
disappeared.  This  confidence  in  the  efficacy  of  isolation  was 
in  the  then  existing  state  of  knowledge  not  unreasonable. 

Isolation  and  its  Results  in  Providence.  —  Previous  to 
1884  there  had  been  in  Providence  no  isolation  to  speak  of 
in  any  of  the  contagious  diseases  except  smallpox.  In  fact 
very  many  physicians  did  not  consider  that  scarlet  fever  and 
diphtheria  were  very  contagious,  if  contagious  at  all,  but 
were  inclined  to  look  upon  them  as  filth  diseases.  Restric- 
tive measures,  including  isolation  at  home  and  fumigation, 
began  to  be  applied  in  1884  and  were  quite  steadily  strength- 
ened during  the  next  sixteen  or  seventeen  years.  I  hoped, 
as  did  most  health  officers,  that  if  scarlet  fever  and  diph- 
theria could  not  be  stamped  out,  they  could  be  reduced  to 
an  insignificant  remnant.  But  they  were  not  stamped  out 
in  Providence,  as  they  have  not  been  in  other  cities.  On  the 
contrary,  we  had  twice  as  many  deaths  in  1887  from  scarlet 
fever  as  we  had  had  during  any  year  for  seven  years.  Diph- 
theria from  1886  to  1890  also  caused  nearly  double  the  num- 
ber of  deaths  that  it  had  in  the  preceding  four  years.  Of 
course  we  talked  about  epidemic  waves,  and  noted  that  the 
mortality  from  the  last  wave  was  very  much  lower  than  from 
many  that  had  preceded  it,  and  congratulated  ourselves  that 
the  outbreak  was  not  so  severe  as  in  former  years.  But  I 
began  to  ask  myself  what  there  was  about  epidemic  waves 
that  made  restrictive  measures  of  little  use,  and  also  to  inquire 
if  there  was  anything  wrong  about  the  restrictive  measures. 
If  we  were  limiting  these  diseases  at  all,  it  was  certainly  in  a 
very  moderate  way. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION     137 

Infection  by  Air  and  Fomites  Thought  Most  Important.  — 

It  was  fully  appreciated  that  in  cities  at  least  most  cases 
of  contagious  disease  cannot  be  traced  to  their  source.  Two 
theories  have  from  antiquity  been  advanced  in  explanation. 
One  is  that  most  contagious  diseases  are  easily  carried 
by  the  atmosphere.  Thus  a  person  going  by  a  house  where 
there  is  scarlet  fever,  or  passing  an  infected  person  in  the 
street,  might  contract  the  disease.  Such  unconscious  exposure 
might  be  quite  common.  But  the  principal  source  of  the 
untraced  cases  of  contagious  disease  was  believed  to  be  fo- 
mites. Walls  and  furniture  were  thought  to  become  infected 
with  the  virus,  and  for  weeks  and  months  persons  entering 
the  room  might  contract  disease  through  the  breath.  Books, 
toys,  clothing  and,  in  fact,  every  material  thing,  might  readily 
become  a  source  of  infection  and  retain  its  virulence  for 
months  and  years.  These  were  perhaps  not  unreasonable 
a  priori  h^'potheses,  and  they  had  some  apparent  backing  of 
facts.  At  any  rate  they  were  the  best  theories  we  had.  So 
health  officers  everywhere,  including  Providence,  set  about 
improving  methods  of  disinfection.  Sulphur  fumigation  was 
abandoned  and  the  use  of  formaldehyde  gas  adopted  in 
its  place.  Many  cities  set  up  a  steam  disinfecting  plant,  in 
Providence  as  early  as  1887,  and  carpets,  bedding  and  cloth- 
ing were  disinfected  by  steam.  Some  cities,  particularly  on 
the  continent  of  Europe,  sent  a  band  of  uniformed  disinfec- 
tors  to  wash  and  scrub  everything  in  the  infected  house. 
Scarlet  fever  and  diphtheria  refused  to  be  exterminated, 
though  in  Providence  we  did  have  rather  less  during  the  early 
nineties  than  we  had  had  before.  But  I  was  not  satisfied. 
It  seemed  to  me  that  we  were  having  too  much  of  these 
diseases,  that  there  must  be  a  leak  somewhere. 

Cultures  Expected  to  Discover  Much  Diphtheria.  —  Then 
for  one  disease  a  new  weapon  was  put  into  our  hands.  Many 
had  long  recognized  that  the  diagnosis  of  diphtheria  was  diffi- 
cult. It  was  suspected  that  many  cases,  because  of  this  diffi- 
culty, escaped  isolation  entirely.    When  the  culture  method 


138        THE  SOURCES  AND  MODES  OF  INFECTION 

of  diagnosis  was  devised  I  became  enthusiastic  and  hopeful. 
We  adopted  it  in  Providence  in  January,  1895,  and  soon  after 
required  a  negative  culture  before  the  patient  was  released 
from  isolation.  Hill  has  shown  that  without  cultures  the 
chance  of  error  in  the  diagnosis  of  diphtheria  is  50  per  cent, 
which  corresponds  entirely  with  my  frequently  expressed 
opinion  before  the  advent  of  the  culture  method.  It  is  evi- 
dent, then,  that  the  general  use  of  cultures  ought  to  bring  to 
light  great  numbers  of  cases  of  diphtheria  which  were  formerly 
unrecognized,  and  this  it  certainly  does.  If  such  an  im- 
provement in  diagnosis,  and  consequently  in  isolation,  is 
brought  about  by  the  use  of  cultures,  and  if  by  the  same  means 
isolation  can  be  maintained  until  the  patient  is  certainly  free 
from  infection,  there  ought  to  follow  a  marked  reduction 
in  this  disease.  But  it  was  quite  otherwise.  The  deaths  in 
Providence,  which  in  1894  had  numbered  45,  rose  to  79  in 
1895  and  125  in  1896,  nearly  twice  as  many  in  proportion  to 
the  population  as  there  were  in  1883,  when  there  was  no  isola- 
tion, no  disinfection  and  no  antitoxin.  The  cases  rose  from 
166  in  1894  to  386  in  1895  and  890  in  1896.  The  apparent 
reduction  in  the  fatality  rate  from  27.71  to  14.07  indicates 
very  plainly  that  the  culture  method  of  diagnosis  had  dis- 
covered a  very  large  number  of  mild  cases  that  would  have 
previously  been  unrecognized,  for  antitoxin  was  only  a  minor 
factor  in  reducing  the  fatality,  as  it  had  been  used  in  only  a 
little  over  one-third  of  the  cases.  Isolation,  disinfection,  the 
use  of  cultures,  and  the  opening  of  the  contagious  hospital 
had  been  accompanied  l)y  the  greatest  prevalence  of  the  dis- 
ease for  ten  years.  I  do  not  mean  to  say  that  the  adoption 
of  the  measures  described  had  no  effect  upon  the  amount 
of  dipiilheria  in  Providence.  I  am  sure  that  they  had,  and 
that  this  disease  on  the  whole  has  been  lessened,  cases  pre- 
vented and  lives  saved.  But  better  results  were  expected. 
I  was  disappointed,  and  I  think  other  health  officers  have 
been  disappointed  also.  It  seemed  that  the  measures,  car- 
ried out  as  they  were,  ought  to  have  given  better  results. 


LIMITATIONS  TO   THE   VALUE  OF  ISOLATION     139 

It  seemed  that  there  was  something  which  we  did  not 
understand. 

Failure  of  Hospital  Isolation.  —  One  of  the  most  effectual 
means  of  isolating  cases  of  contagious  diseases  is  by  removal 
to  the  hospital.  Certainly  while  in  the  hospital  they  can  do 
no  harm,  and  with  reasonable  care  there  is  not  much  danger 
of  their  carrying  infection  back  to  their  homes.  Return  cases 
do  not  occur  in  scarlet  fever  and  diphtheria  in  more  than 
about  one  to  three  per  cent  of  discharges,  and  are  not  a  factor 
of  moment  in  the  extension  of  these  diseases.  The  idea  that 
such  hospitals  would  be  a  powerful  factor  in  the  extermina- 
tion of  these  diseases  was  not  unreasonable.  Smallpox  hos- 
pitals have  been  in  general  use  for  a  very  long  time,  but  they 
are  not  here  under  consideration,  though  it  is  questionable 
whether  the  hospital  isolation  of  smallpox  can  ever  accom- 
plish much  alone  and  unaided  by  vaccination.  But  it  is  the 
hospitalization  of  scarlet  fever  and  diphtheria  that  is  par- 
ticularly .instructive. 

English  Hospitals.  —  The  use  of  hospitals  for  contagious 
diseases  has  been  carried  farther  in  England  than  elsewhere. 
Fifteen  or  twenty  years  ago  the  larger  municipalities  began 
building  them  on  a  considerable  scale,  and  at  present  most 
of  the  English  towns  are  provided  with  large  hospitals  for 
scarlet  fever,  and  to  a  less  extent  for  diphtheria.  At  the  time 
when  their  construction  was  first  strongly  urged  it  was  be- 
lieved that  their  use  would  result  in  the  eradication  of  the 
diseases  for  which  they  were  provided.  The  result  has  cer- 
tainly been  disappointing,  and  there  has  recently  been  an 
active  discussion  as  to  whether  they  do  an  amomit  of  good  in 
restricting  disease  at  all  commensurate  with  their  cost.^  There 
is  no  doubt  that  the  mortality  from  scarlet  fever,  both  in 

1  O'Connor,  Geo.  Wilson,  Waddy  and  others,  Brit.  M.  J.,  Lond.,  1905| 
II,  630;  Millard,  Biss,  Fraser,  etc.,  Med.  Press  &  Circ,  Lond.,  1904, 
LXXVIII,  215,  218,  241,  327,  377;  Newsholme,  Tr.  Epidem.  Soc. 
Lond.,  n.  s.,  1900-01,  XX,  48;  J.  Hyg.,  1901,  I,  145;  Millard,  Pub. 
Health,  1901,  XIII;  J.  T.  Wilson,  Pub.  Health,  1896-97,  IX,  Sup.,  p.  21. 


140        THE  SOURCES  AND  MODES  OF  INFECTION 

England  and  the  United  States,  has  greatly  diminished  during 
recent  years,  but  whether  this  has  been  due  to  restrictive 
measures  or  to  lowered  virulence  has  been  disputed.  The 
small  death  rate  would  indicate  that  the  disease  is  really 
milder.  This  is  also  indicated  by  the  fact  that  plural  deaths, 
that  is,  more  than  one  death  in  a  family,  are  less  frequent 
now  than  formerly.  Again,  local  outbreaks  of  the  old-time 
severe  type  occasionally  appear.  There  was  such  an  out- 
break in  Providence  in  1906-07,  during  which  the  case  fatal- 
ity ran  up  to  12.85  per  cent.  Similar  outbreaks  have  been 
noted  in  Keene,  N.  H.,  Haverhill,  Worcester  and  Mont- 
real. The  relatively  lowered  fatality  in  recent  years  has 
rendered  it  difficult  to  determine  from  the  number  of  deaths 
just  what  influence  restrictive  measures,  like  hospital  isola- 
tion, have  had  on  the  prevalence  of  scarlet  fever,  and  increas- 
ing accuracy  and  care  in  reporting  cases  render  it  difficult 
to  draw  conclusions  from  the  number  of  cases.  But  after 
all  has  been  said  it  is  clear  that  hospital  isolation  in  scarlet 
fever  has  checked  the  disease  very  much  less  than  was  ex- 
pected, and  sometimes  appears  to  have  had  little  effect.  In 
Huddersfield,  a  city  of  nearly  one  hundred  thousand  people, 
from  1890  to  1899  the  percentage  of  removals  to  the  hospital 
was  90,  yet  the  mean  attack  rate  for  the  period  was  4.3  per 
thousand.  From  1900  to  1908  the  removals  to  the  hospital 
were  92.4  per  cent  and  the  attack  rate  2.96.  This  is  certainly 
a  surprisingly  high  morbidity  rate  for  a  city  where  practically 
all  reported  cases  have  for  twenty  years  been  subjected  to 
most  excellent  isolation.  A  similar  state  of  things  is  noted 
in  other  cities.  Some  cities  with  a  high  per  cent  of  removals 
to  the  hospital  have  more  of  the  disease  than  do  cities  with 
no  hospitals.  The  same  is  noted  in  rural  communities. 
O'Connor,'  medical  officer  of  health  of  Leicestershire  and  Rut- 
land combined  sanitary  districts,  reported  that  in  five  par- 
ishes where  the  percentage  of  hospital  isolation  had  for  ten 
years  reached  66  per  cent,  the  attack  rate  was  6.2  per  thou- 
'  O'Connor,  Brit.  M.  J.,  Lond.,  1905,  II,  630. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION     141 

sand,  while  in  five  other  parishes  where  hospital  isolation  was 
applied  to  only  14  per  cent  of  the  cases,  the  attack  rate  was 
2.8.  In  another  district,  one  parish  which  sent  60  per  cent  of 
its  scarlet  fever  to  the  hospital,  had  three  times  as  many 
cases  as  contiguous  parishes  which  had  little  hospital  isola- 
tion. Neech^  says  that  in  Cornwall  from  1898  to  1907  there 
was  practically  no  difference  in  the  incidence  of  scarlet  fever, 
in  both  urban  and  rural  districts,  connected  with  the  use  or 
failure  to  use  isolation  hospitals.  Again,  a  city  after  it  builds  a 
hospital  maj^have  more  of  the  disease  than  before.  The  aban- 
donment of  hospital  isolation  may  do  no  harm.  In  Leices- 
ter- the  hospital  was  closed  temporarily,  and  all  the  scarlet 
fever  cases  sent  to  their  homes,  with  an  actual  decrease  in 
number  of  reported  cases.  The  hospital  in  other  cities  also 
has  been  closed  without  harm.  I  have  thought  it  possible 
that  at  times  hospital  isolation  might  actually  favor  the 
spread  of  disease.  When  a  case  is  removed  to  the  hospital, 
comparatively  little  restraint  is  placed  upon  other  members 
of  the  family,  and  if  some  of  them  are  carriers,  as  they  cer- 
tainly usually  are  in  diphtheria,  much  harm  may  result.  If, 
however,  the  case  is  kept  at  home,  the  rest  of  the  family, 
particularly  the  children,  are  under  considerable  restraint  for 
several  weeks.  Observations  in  Providence  demonstrate  that 
the  retention  of  the  case  at  home  very  rarely  leads  tothe 
extension  of  the  disease  to  other  families  in  the  house,  and 
presumably  to  still  less  extension  outside  of  the  house. 

Why  the  Failure  ?  —  It  may  be  admitted,  and  is  doubtless 
true,  that  hospitals  have  prevented  very  msmy  cases  of  dis- 
ease, and  they  may  have  been  somewhat  of  a  factor  in  its 
lessened  prevalence.  Nevertheless  it  must  also  be  admitted 
that,  notwithstanding  the  complete  and  excellent  isolation 
secured  in  some  cities  like  Huddersfield,  scarlet  fever  has 
still  prevailed  to  an  alarming  extent.  When  eighty  to  ninety 
per  cent  of  the  cases  are  removed  to  the  hospital  it  is  certain 

'  Neech,  Pub.  Health,  Lond.,  1908-09,  XXII,  296. 
*  Rep.  on  Health  of  Leicester,  1902,  36. 


142        THE  SOURCES  AND  MODES  OF  INFECTION 

that  the  remainder  will  be  so  situated  that  home  isolation  will 
quite  effectually  prevent  extension  from  them.  In  such  cities 
almost  all  of  the  reported  cases  are  thus  effectively  isolated, 
either  in  hospital  or  home.  Yet  the  disease  continues  to  pre- 
vail. There  is  evidently  some  source  which  escapes  control. 
Newsholme  has  very  clearly  shown  this.  While  admitting 
that  isolation  does  prevent  much  sickness,  he  says  that  the 
disease  still  prevails  and  outbreaks  still  occur  owing  to  some 
"epidemic  influence."  Now  our  purpose  is  to  determine,  if 
possible,  what  this  "epidemic  influence"  is.  What  is  the 
factor  which  is  so  powerful  and  continuous  in  its  action  that 
90  to  95  per  cent  of  perfection  in  the  isolation  of  a  contagious 
disease  is  unable  to  prevent  a  continued  high  prevalence  and 
repeated  epidemic  waves  ? 

American  Hospital  Experience.  —  It  is  not  merely  English 
hospital  experience  which  has  shown  the  inefficiency  of  isola- 
tion. We  have  numerous  instances  in  our  own  country.  I 
have  alread}^  referred  to  the  experience  of  Providence,  where 
increasing  stringency  in  isolation  was  not  followed  by  a 
decrease  in  contagious  diseases.  There  has  been  much  dif- 
ference between  American  cities  as  regards  the  strictness  of 
enforced  isolation.  Some  have  been  notoriously  lax,  while 
others  have  for  years  endeavored  to  secure  a  complete  regis- 
tration of  scarlet  fever  and  diphtheria,  and  have  adopted 
rigorous  measures  of  isolation  and  disinfection,  though  in  no 
American  city  has  hospitalization  been  carried  so  far  as  it  has 
in  many  English  towns.  But  no  one  would  be  able,  by  study- 
ing mortality  rates,  to  pick  out  the  cities  which  pursue  a 
rigorous  policy  of  isolation.  I  collected  data  relating  to  the 
prevalence  of  scarlet  fever  and  diphtheria  in  American  cities 
for  the  decade  1890-1899,'  and  it  is  surprising  to  note  that 
the  cities  with  the  best  sanitary  administration  frequently 
have  a  comparatively  large  amount  of  scarlet  fever  and  diph- 
theria. During  the  period  mentioned,  Boston,  in  my  opinion, 
had  the  best  sanitary  administration  of  any  of  the  large  cities, 

*  Chapin,  Municipal  Sanitation,  Providence,  1901,  Table  op.  480. 


LIMITATIONS   TO   THE   VALUE  OF  ISOLATION      143 

though  New  York  stood  high.  The  death  rate  from  diph- 
theria in  both  cities  was  84  per  100,000  living,  from  scarlet 
fever  25  for  Boston,  and  33  for"  New  York.  Certainly  neither 
Chicago  nor  Cincinnati  enforced  such  rigorous  measures,  yet 
the  rates  in  these  two  cities  were  72  and  71  for  diphtheria 
and  17  and  7  for  scarlet  fever.  Among  the  smaller  Mas- 
sachusetts cities  Fall  River  has  usually  had  a  rather  ineffi- 
cient health  service  and  little  hospitalization,  yet  the  death 
rate  from  diphtheria  was  21  and  from  scarlet  fever  15  per 
100,000  living,  while  in  Worcester  the  figures  were  48  and  8, 
and  this  notwithstanding  the  fact  that  in  Fall  River  the 
proportion  of  children  is  much  greater  than  in  most  Amer- 
ican cities,  and  that  the  population  is  exceptionally  ignorant 
as  measured  by  illiteracy.  Worcester  has  had  a  contagious- 
disease  hospital  since  1897,  and  has  removed  to  it  in  some 
years  as  high  as  63  per  cent  of  its  diphtheria  cases.  In  general, 
Worcester  secures  an  excellent  registration  of  cases,  and  con- 
sequent isolation.  Nevertheless  Worcester  has  recently  had, 
notwithstanding  its  increasing  hospitalization  and  good  home 
isolation,  a  severe  outbreak  of  the  disease.  It  seems  a  fair 
assumption  that  some  factor  much  more  important  than  the 
recognized  cases  of  the  disease  has  been  at  work  in  Worcester. 
If  it  were  not  so,  the  reported  cases  of  the  disease  should  not 
have  risen  from  132  in  1905  to  1178  in  1907. 

Diphtheria  Isolation  at  Home.  —  In  Providence  for  some 
years  previous  to  March,  1902,  isolation  in  diphtheria  was 
terminated  only  when  a  negative  culture  had  been  obtained 
from  the  patient.  At  that  date  a  change  was  made,  terminat- 
ing isolation  ten  days  after  the  disappearance  of  exudation. 
This  certainly  liberated  many  cases  still  infectious,  but  this 
factor  was  of  so  little  moment  that  the  disease  continued  to 
decrease  until  on  a  certain  day  in  August  the  city  was  entirely 
free  from  reported  cases,  a  condition  again  nearly  reached  in 
1907. 

Isolation  in  Institutions.  —  It  is  by  no  means  uncommon 
to  see  outbreaks  in  institutions  lasting  many  months,  al- 


144        THE  SOURCES  A.YD  MODES  OF  INFECTION 

though  every  case  is  promptly  isolated  and  all  persons  in  the 
institution  are  repeatedly  examined  by  cultures  from  throat 
and  nose.  I  have  records  of  several  such  in  Providence,  and 
most  health  officers  and  managers  of  institutions  have  been 
through  such  unpleasant  experiences.  Here  again  we  are 
forced  to  look  for  sources  other  than  the  recognizable  cases. 

At  a  school  in  Owatonna,  Minnesota/  there  had  been  more 
or  less  diphtheria  for  years  until  a  sharp  outbreak  in  1896 
caused  a  very  energetic  effort  to  be  made  to  stamp  it  out. 
Cultures  were  taken  from  everybody,  and  all  persons  in  whom 
diphtheria  bacilli  were  found  were  isolated,  at  first  in  a  com- 
mon ward,  but  later  each  person  in  a  separate  room.  Isola- 
tion was  maintained  until  three  successive  negative  cultures 
were  obtained  from  throat  and  nose,  and  efficient  disinfection 
was  practiced.  Still  the  disease  persisted  month  after  month, 
and  some  of  the  carriers,  after  release,  were  found  to  be  still 
harboring  the  bacilli.  One  boy  carried  the  bacilli  for  nineteen 
months.  The  attempt  at  the  isolation  of  carriers  was  aban- 
doned, and  several  years  later  there  was  still  more  or  less 
diphtheria  in  the  institution. 

A  still  more  notable  failure  of  the  isolation  of  diphtheria 
was  at  the  Willard  State  Hospital  for  the  insane  in  New  York.^ 
In  this  institution  practically  the  same  methods  were  adopted 
as  at  Owatonna,  but  nevertheless  the  disease  persisted  sev- 
eral years.  Patients  and  carriers  released  from  isolation  after 
several  negative  cultures  were  still  found  to  be  carriers.  If 
in  an  institution  of  this  kind,  where  the  strictest  discipline 
is  maintained,  and  where  carriers  can  be  isolated  indefinitely, 
the  most  stringent  measures  of  isolation  and  disinfection  fail 
to  stamp  out  the  disease,  what  is  to  be  expected  of  any  such 
measures  which  can  be  adopted  in  an  ordinary  community? 

An  outbreak  in  a  hospital  in  California  was  managed  in 

>  St.  Paul  M.  J.,  1900,  II,  223;  Brit.  M.  J.,  Lond.,  1898,  I,  1008;  Rep. 
St.  B(l.  Tfcalth,  Minnesota,  1897-98,  465;  Kop.  Am.  Pub.  Health  Ass., 
1899,  XXV,  .540. 

*  Rep.  State  Commission  in  Lunacy,  N.  Y.,  1904,  XVI. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION     145 

the  same  way.^  At  first  no  effect  seemed  to  be  produced, 
and  the  outbreak  lasted  from  April  to  August,  but  was  as- 
sumed to  have  been  finally  checked  by  the  same  measures 
which  failed  at  Owatonna  and  Willard.  But  as  many  out- 
breaks last  even  a  shorter  time,  though  no  attention  is  paid 
to  carriers,  it  is  uncertain  whether  the  outbreak  was  stamped 
out  or  ched  out.  Sidney  Davies^  reports  that  at  the  Bostall- 
lane  School  in  Woolwich  diphtheria  prevailed  for  three  years 
notwithstanding  repeated  closures  and  bacterial  examinations 
of  the  pupils.  There  is  little  doubt  that  at  times  a  careful 
search  for  carriers  and  missed  cases  in  schools  and  institu- 
tions and  their  isolation  until  two  successive  negative  cul- 
tures from  throat  and  nose  are  obtained,  prove  successful  in 
checking  outbreaks;  there  is  no  doubt,  too,  that  outbreaks 
frequently  die  out  of  themselves;  and  it  is  shown  by  the  exam- 
ples given  above  that  it  is  at  times  impossible  by  any  degree 
of  isolation  to  stamp  out  an  outbreak.  How  to  manage  such 
institutional  epidemics  cannot  be  determined  until  the  con- 
trol of  carriers  is  more  carefully  studied  than  it  has  been. 

Isolation  a  Failure  in  Measles.  —  Measles  is  a  disease 
which  in  cities  it  seems  to  be  impossible  to  check  to  any 
appreciable  extent  by  isolation.  In  Aberdeen  ^  this  was  faith- 
fully tried  for  twenty  years,  1883  to  1902,  but  no  apparent 
effect  was  produced  on  the  prevalence  of  the  disease.  Similar 
failures  have  been  noted  elsewhere.  During  the  last  half  of 
this  period  in  Aberdeen,  when  there  was  far  more  accurate 
registration  and  better  control  than  before,  the  number  of 
cases  rose  to  24,254,  about  fifty  per  cent  more  than  in  the  first 
half  of  the  period.  A  census  of  the  children  in  certain  schools 
indicated  that  from  ninety  to  ninety-three  per  cent  of  children 
over  ten  years  of  age  had  had  the  disease.  Restrictive  meas- 
ures which  protected  only  seven  to  ten  per  cent  of  the  popu- 
lation from  attack  were  then  wisely  abandoned.     The  very 

1  Rep.  State  Bd.  of  Health,  California,  190&-08,  201. 

2  Rep.  Med.  Off.  Health,  Lond.,  1908,  36. 

3  Aberdeen,  Report  of  Med.  Off.  of  Health,  1904,  41. 


146         THE  SOURCES  AND  MODES   OF   INFECTION 

excellent  report  of  the  medical  officer  of  health  of  Aberdeen 
discusses  the  subject  very  fully.  In  New  York  measles  was 
first  isolated  in  1896,  but  not  until  1902  were  the  regulations 
very  rigorously  enforced.  The  average  death  rate  from  1895 
to  1904  was  2.40,  and  the  highest  death  rate  since  1896  was 
reached  in  1906,  when  it  was  2.69.  There  is  no  evidence  that 
the  measures  adopted  in  New  York  have  had  any  more 
influence  on  the  prevalence  of  the  disease  than  did  isolation 
and  disinfection  in  Aberdeen.  It  seems  in  the  highest  degree 
probable  that  the  disease  prevails  because  of  the  unrecognized 
but  infectious  prodromal  stage.  No  amount  of  isolation  after 
the  disease  is  recognized  can  atone  for  the  harm  done  before 
the  diagnosis  is  made. 

Isolation  a  Failure  in  Meningitis.  —  AVithin  a  recent  period 
the  city  of  New  York  suffered  from  an  exceptionally  long  and 
severe  outbreak  of  cerebro-spinal  meningitis.  The  attack 
rate  was  higher  than  in  any  of  the  other  large  American  cities, 
and  the  outbreak  lasted  longer;  and  it  lasted  longer  than  it 
has  in  most  of  the  German  cities.  On  April  19,  1905,  after 
the  epidemic  had  continued  for  about  two  years,  very  strin- 
gent restrictive  measures  of  isolation  and  disinfection  were 
adopted.  The  outbreak  was  then  declining,  and  that  it  would 
afterwards  decline  still  more  was  to  have  been  expected. 
But  it  was  not  "stamped  out,"  for  in  1907  there  were  reported 
042  deaths  and  in  1908,  351.  In  Leith  ^  great  efforts 
were  made  to  isolate  all  suspects  and  carriers,  and  the 
outbreak  appeared  to  be  chocked,  but  in  Edinburgh  also 
it  died  out,  though  without  such  energetic  measures.  The 
experience  in  Germany  seems  to  l)e  that  if  in  the  beginning 
diligent  search  is  made  for  carriers,  and  stri(!t  isolation  is 
maintained,  the  outbreak  may  sometimes  be  checked,  but 
after  the  (Hscase  has  bcM'ome  established,  and  carriers  are 
numc^rous,  isolation  is  of  litth;  avail.  These  appear  to  be 
the  views  of  Lingelsheim,  Ostermann,  Selter,  Flatten  and 
others. 

1  Kor.  I'nu-I.itioncr,  T.ond.,  lOOS,  LXXX,  66. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION      147 

Isolation  often  a  Failure  in  Smallpox.  —  Smallpox  is  less 
likely  to  escape  detection  than  is  any  other  disease.  Yet 
epidemics  grow  in  the  face  of  the  most  rigid  isolation.  Unrec- 
ognized cases,  even  in  this  disease,  are  so  numerous  that  the 
isolation  of  the  recognized  cases  often  seems  to  be  a  complete 
failure.  The  State  Board  of  Health  of  Minnesota,  realiz- 
ing this,^  has  had  the  boldness  to  advise  that  no  attempt  be 
made  to  isolate,  and  that  entire  reliance  be  placed  on  vacci- 
nation. It  was  hoped  that  this  would  lead  to  more  complete 
vaccination.  There  has  been  no  alarming  increase  in  small- 
pox in  Minnesota,  and  Montana  ^  is  now  following  the  lead 
of  the  former  state. 

Why  Does  Isolation  Fail  ?  —  The  epidemiological  evidence 
is  conclusive  that  the  isolation  of  recognized  cases  of  con- 
tagious diseases  often  fails  to  check  outbreaks  which  grow 
in  spite  of  it;  that  it  does  not  stamp  out  disease,  and  that  it 
only  reduces  in  a  moderate  degree  the  prevalence  of  the 
disease.  We  are  forced  to  conclude  that  there  is  some  defect 
in  our  procedures,  or  some  other  source  of  infection  more 
important  than  the  recognized  cases.  The  error  cannot  be 
that  isolation  is  too  brief,  for  return  cases  and  recurrences 
are  not  important  factors.  It  is  not  that  isolation  is  imper- 
fect, for  isolation  in  the  hospital  is  well-nigh  complete,  and 
careful  observations  in  Providence  indicate  that  the  danger 
of  extension  outside  the  family  from  cases  at  home  is  very 
slight. 

Importance  of  Carriers  and  Missed  Cases.  —  As  has  been 
previously  stated,  two  theories  have  been  advanced  to  account 
for  the  appearance  of  untraced  cases  of  contagious  diseases: 
that  of  distant  aerial  infection,  and  that  of  the  persistence  of 
infection  on  things,  i.e.,  fomites.  In  other  chapters  of  this 
book  it  is  shown  that  both  of  these  modes  of  infection  are 
of  little  moment,  and  in  the  first  chapter  it  was  shown  to  be 

1  Resolution  adopted  July,   1906,  to  go  into  effect  January,  1908, 
Am.  J.  Pub.  Hyg.,  1907,  III,  227. 
^  Am.  J.  Pub.  Hyg.,  1909,  V,  815. 


148         THE  SOURCES  AND  MODES  OF  INFECTION 

unlikely  that  the  specific  organisms  of  our  common  diseases 
grow  outside  of  the  body.  In  the  second  chapter  it  was 
shown  that  they  may  grow  in  the  body  and  yet  produce  few 
or  no  symptoms.  It  appears,  then,  highly  probable  that  by 
far  the  most  important  factor  in  the  causation  of  the  con- 
tagious diseases  are  the  ''carrier"  and  ''missed"  cases. 

It  is  not  for  a  moment  suggested  that  the  existence  of 
carriers  explains  all  epidemiological  problems.  There  are,  for 
instance,  quite  a  number  of  contagious  diseases  which  exhibit 
a  varying  degree  of  periodicity.  We  have  as  yet  only  the 
vaguest  notions  as  to  the  causes  of  the  variations  in  the 
prevalence  of  disease,  its  seasonal  irregularities,  and  the  rise 
and  fall  of  epidemics.  There  is  no  reason  to  believe  that 
these  phenomena  depend  on  the  extra-corporal  growth  of 
pathogenic  organisms,  and  it  is  probable  that  the  seasonal 
distribution  of  such  diseases  as  smallpox  and  scarlet  fever  is 
only  in  the  most  indirect  manner  dependent  upon  tempera- 
ture, rainfall,  etc.  It  is  not  unlikely  that  the  factors  affecting 
the  extension  of  these  diseases  are  so  numerous  that  their 
prevalence  is  really  to  a  large  extent  a  matter  of  chance. 
But  whatever  the  factors  may  be,  we  must  believe  that  they 
affect  carriers  as  well  as  clinical  cases.  Why  we  have  more 
carriers  and  more  cases  at  one  time  than  another,  we  cannot 
at  present  say.  But  it  appears  to  be  in  the  highest  degree 
probable;  that  in  times  of  outbreaks,  as  well  as  in  inter- 
epidemic  periods,  the  chief  factor  in  the  extension  of  the 
disease  is  the  existence  of  unrecognized  infection  in  human 
beings  or,  in  some  diseases,  in  the  lower  animals. 

Need  of  Further  Study.  —  I  would  be  the  last  person  to 
assert  that  the  views  here  set  forth  are  unassailable  and  unal- 
terable. They  doubtless  will  be  modified;  it  may  be  that 
they  are  entirely  erroneous.  What  is  needed  is  further  inves- 
tigation along  the  lines  indicated,  and  a  great  deal  of  it. 
Unfortunately  sanitary  science  is  far  from  exact.  We  have 
few  established  truths,  but  many  theories  of  greater  or  less 
probability,  on  which  to  base  our  practice.    The  probability 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION      149 

of  each  theory  must  be  carefully  weighed.  Which  is  the  most 
probable  source  of  infection,  the  cesspool  in  the  yard,  the 
fomites  that  escaped  disinfection,  the  patient  who  was  re- 
leased too  soon,  or  the  unknown  carrier  ?  The  chances  are 
greatly  in  favor  of  the  last,  and  yet  to-day  sanitary  practice 
almost  completely  ignores  the  carrier.  It  is  not  surprising 
that  many  health  officers  fail  to  appreciate  the  importance 
of  the  question  which  is  here  discussed.  It  is  remarkable, 
however,  that  bacteriologists  as  a  rule  minimize  the  danger 
to  be  apprehended  from  carriers. 

Carriers  not  to  be  Ignored.  —  It  may  be  admitted  that 
only  1  per  cent  of  the  population  are  diphtheria  carriers, 
though  as  a  matter  of  fact  it  must  often  be  more  than  that; 
also  that  only  15  per  cent  of  these  carry  virulent  germs,  though 
it  is  really  often  much  greater.  It  may  also  be  admitted  that 
these  bacilli  are  not  usually  so  numerous  as  in  the  sick,  though 
it  is  known  that  they  sometimes  appear  in  pure  culture;  yet 
even  admitting  all  this,  there  will  be  in  inter-epidemic  periods 
in  a  city  of  100,000  people  at  least  150  well  persons  carrying 
virulent  diphtheria  bacilh.  Why  should  the  bacteriologist 
ignore  these  150  sources  of  infection  and  insist  on  two  throat 
and  nose  negative  cultures  from  every  reported  patient  ?  Or 
why  should  he,  as  he  occasionally  does,  recommend  isolating 
the  carriers  in  the  family  but  ignore  all  other  carriers  ?  Why 
neglect  this  whole  question  of  carriers,  and  spend  endless  time 
in  devising  methods  of  liberating  formaldehyde  to  kill  the 
few  bacilli  that  may  remain  about  the  house  ?  Why  worry 
about  the  saliva  that  may  have  gotten  onto  a  book,  a  coat, 
or  the  wall  of  a  room,  and  neglect  the  reader  of  the  book, 
the  wearer  of  the  coat  and  the  dweller  in  the  room,  who  is 
probably  growing  the  germs  in  his  throat  and  nose  ?  It  is 
not  easy  to  answer  these  questions,  and  so  the  bacteriologist 
withdraws  to  his  laboratory  and  ingores  them.  But  the 
health  officer  must  answer  them  in  one  way  or  another. 

Principles  of  Diphtheria  Isolation.  —  To  confine  the  dis- 
cussion for  the  moment  to  diphtheria,  concerning  which  we 


150        THE  SOURCES  AND  MODES  OF  INFECTION 

have  more  accurate  knowledge  than  we  have  for  any  other 
disease,  there  appear  to  be  only  two  logical  positions  which 
the  health  officer  can  take  in  regard  to  its  management. 
There  is  the  possible  policy  of  non-regulation.  This  the  public 
would  certainly  not  permit,  and  I  think  with  very  good 
reason.  Or  we  can  go  to  the  other  extreme  and  attempt  to 
isolate  every  person  carrying  diphtheria  bacilli,  until  they 
disappear  from  throat  and  nose,  or  until  they  are  shown  to  be 
non-virulent.  That  is,  of  course,  entirely  impracticable  except 
in  small  isolated  communities  or  institutions,  and  it  is  often 
very  difficult,  and  sometimes  impossible  then.  In  every  large 
city  there  are  hundreds  of  carriers  who  can  never  be  detected, 
and  who  could  not  be  controlled  if  they  were.  Virulent  bacilli 
may  remain  for  months,  and  the  attempt  to  isolate  for  a  pro- 
longed period  prominent  lawyers,  business  men,  or  physi- 
cians, would  result  in  a  breakdown  of  the  whole  system. 
As  a  matter  of  fact,  such  carriers  escape  from  isolation  while 
still  infected.  If  cultures  are  taken  daily,  or  every  few  days, 
it  is  usually  not  very  long  before  the  two  negatives  required 
by  rule  are  secured  and  the  patient  is  released,  though  sub- 
sequent cultures  not  infrequently  reveal  the  bacillus.  The 
ideal  of  health  officers  has  been  to  keep  up  isolation  until 
every  spark  of  infection  has  died  out,  —  a  very  reasonable 
ideal,  until  it  was  learned  that  there  are  many  hidden  sparks 
scattered  about  the  community,  some  of  which  are  sure  sooner 
or  later  to  burst  into  flame.  As  it  is  impossible  to  attain  the 
ideal  of  stamping  out  all  infection,  and  as  it  is  certain  that 
many  infected  persons  cannot  be  restrained  at  all,  it  is  unrea- 
sonable to  require  restraint  to  the  uttermost  limit,  of  the 
recognized  cases.  It  is  often  argued  that  the  fact  that  all 
infected  persons  cannot  be  isolated,  is  no  reason  for  not  iso- 
lating all  that  can  be  found,  anymore  than  the  fact  that  many 
thieves  escape  is  no  reason  for  not  imprisoning  those  thieves 
who  are  caught.  But  there  is  no  true  parallel  here.  The 
thief  is  a  criminal,  and  his  imprisonment  is  a  punishment. 
Tlie  bacillus  carrier  is  not  a  criminal,  and  he  is  isolated,  not 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION      151 

as  a  punishment,  but  to  protect  the  community.  If  the 
protection  secured  is  not  commensurate  with  the  hardship 
inflicted,  the  procedure  is  unjust,  and  unwise  from  a  socio- 
logical standpoint. 

A  Compromise  Necessary.  —  But  just  as  soon  as  we  depart 
from  the  orthodox  ideal,  absolute  isolation,  we  have  to  adopt 
some  sort  of  compromise,  a  compromise  which  has  no  strictly 
logical  defense.  We  are  thus  forced  to  follow  one  of  three 
policies,  —  either  do  nothing,  which  is  unwise  and  would  not 
be  permitted,  or  attempt  absolute  isolation  of  all  sources 
of  infection,  which  is  manifestly  impossible,  or  employ  a 
moderate  degree  of  restriction,  which,  though  not  strictly 
logical,  is  nevertheless  practicable,  reasonable  and  to  a  con- 
siderable degree  effective. 

Isolation  of  Real  Value.  —  While  the  most  rigorous  isola- 
tion does  not  stamp  out  diphtheria,  we  know  that  restriction 
does  some  good.  The  removal  of  a  case  to  the  hospital  is 
shown  by  statistical  evidence  to  prevent  to  some  extent  the 
development  of  secondary  cases  in  the  family.  So  too  does 
good  isolation  at  home.  The  warning  sign  on  the  house 
keeps  out  many  people,  some  of  whom  would  otherwise  cer- 
tainl}^  contract  the  disease.  The  regulation  of  school  attend- 
ance prevents  some  school  outbreaks,  and  others  are  checked 
by  the  prompt  removal  of  the  infecting  child.  The  evidence 
points  to  an  appreciable  reduction  in  diphtheria  prevalence 
in  recent  times,  which  I  believe  it  is  fair  to  consider  as  due, 
in  part  at  least,  to  deliberate  separation  of  the  sick  from  the 
well  under  the  direction  of  the  sanitary  authority  or  other- 
wise. Why  more  has  not  been  accomplished  by  isolation  is 
explained  by  the  facts  set  forth  in  the  preceding  chapter. 
If  because  of  the  existence  of  so  many  unrecognized  sources 
of  infection,  isolation  can  effect  only  a  limited  degree  of  pre- 
vention, could  not  substantially  as  much  be  accomplished 
by  more  moderate  methods  than  are  usually  employed  ? 
Why  keep  the  patient  indoors  for  six  weeks  when  other  mem- 
bers of  the  family  with  infected  throats  are  going  about  ? 


152         THE  SOURCES  AND  MODES  OF  INFECTION 

Why  keep  from  work  the  wage  earners  in  an  infected  family 
when  scores  of  other  carriers  are  attending  to  their  business 
without  restraint  ? 

T3T)hoid  Carriers  cannot  be  Isolated,  —  The  isolation  of 
typhoid  carriers  is  no  more  possible,  just,  or  effectual  in  check- 
ing disease,  than  is  the  isolation  of  diphtheria  carriers.  As 
was  shown  in  the  preceding  chapter,  the  number  of  carriers 
and  convalescents  excreting  bacilli  is  probably  much  larger 
than  the  number  of  cases  confined  indoors.  It  seems  to  me 
useless  to  attempt  to  confine  convalescents  two  or  three 
months  after  their  recovery.  There  certainly  would  be  most 
energetic  opposition  on  the  part  of  the  public,  which  probably 
would  ultimately  be  sustained  by  the  courts.  The  health 
officer  who  attempted  to  isolate  convalescents  until  bacilli 
were  no  longer  to  be  found  in  their  urine,  would  be  in  an 
awkward  position  if  he  allowed  chronic  carriers  to  go  at  large, 
and  he  would  be  in  a  still  more  awkward  position  if  he  at- 
tempted to  isolate  all  chronic  carriers  indefinitely.  There 
are  probably  200,000  cases  of  typhoid  fever  in  the  United 
States  each  year,  and  3  per  cent  of  these  would  be  6,000. 
To  attempt  to  isolate  6,000  carriers  would  of  course  be  futile. 
Not  one-tenth  of  them  could  even  be  discovered.  To  isolate 
the  small  fraction  of  carriers  who  can  be  discovered  is  practi- 
cally useless,  and  therefore  unjust.  It  may  be,  and  probably 
is,  wise  to  regulate  the  life  of  such  carriers  as  may  be  dis- 
covered, and  at  times  to  forbid  their  engaging  in  certain 
occupations,  such  as  those  of  cook,  waitress  and  milk  dealer, 
but  to  attempt  their  isolation  under  present  conditions  seems 
to  me  most  unwise. 

Isolation  too  Rigorous.  —  I  believe  that,  on  the  whole,  iso- 
lation in  our  prevailing  contagious  diseases  is  carried  farther 
than  is  necessary;  that  less  rigorous  measures  would  accom- 
plish practically  as  much  good,  and  that  there  would  be  less 
temptation  to  conceal  cases  and  to  interpret  doubtful  symp- 
toms in  line  with  the  patient's  desires.  It  is  impossible  here 
to  lay  down  in  detail  a  scheme  for  the  proper  isolation  of 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION       153 

contagious  diseases.  What  are  the  best  methods  of  dealing 
with  these  diseases  is  a  matter  for  free  discussion,  and  also 
for  experiment.  It  is  to  call  attention  to  the  new  facts,  and 
to  elicit  discussion  from  the  new  viewpoints,  that  these  pages 
are  written. 

Degree  of  Contagiousness.  —  Before  considering  some  of 
the  principles  which  should  guide  the  application  of  meas- 
ures of  isolation,  we  should  consider  what  are,  under  the 
ordinary  conditions  of  life,  the  chances  of  infection  from  a 
single  individual.  Until  recently  it  has  been  believed  to  be 
very  great.  That  smallpox  hospitals  are  placed  a  mile  or 
more  from  inhabited  districts,  that  physicians  clothe  them- 
selves with  gowns  and  caps  and  rubber  boots  on  their  visits 
to  infectious  cases,  and  that  it  is  insisted  that  the  ceiling  of 
a  room  occupied  by  such  a  case  be  disinfected,  indicate  a 
belief  that  the  virus  of  the  contagious  diseases  is  exceedingly 
diffusive  and  exceedingly  virulent.  Why  such  a  belief  is  not 
well  founded  will  be  shown  in  succeeding  chapters,  and  it 
will  suffice  here  to  call  attention  to  the  fact  that  the  chance 
of  an  infected  person  transmitting  the  infection  to  another 
is  not  nearly  so  great  as  is  generally  supposed.  This  is  a 
mathematical  necessity.  We  now  know  that  the  number  of 
infected  persons  is  very  much  greater  than  was  formerly 
believed,  and  that  they  often  remain  infected  for  much  longer 
periods  than  was  suspected.  It  necessarily  follows  that  the 
danger  to  be  apprehended  from  any  one  person  at  any  one 
time  is  much  less  than  was  once  thought. 

Factors  Involved.  —  The  chance  of  an  infected  person  giv- 
ing rise  to  the  disease,  or  of  transmitting  the  infection  to 
others,  varies  greatly  with  the  intensity  of  the  infection,  or 
the  number  of  disease  germs  in  the  secretions  or  excre- 
tions, their  virulence,  the  volume  of  the  excretions,  the  care 
exercised,  the  occupation,  and  the  surroundings  generally. 
Conditions  in  the  home  and  in  institutions  are  usually  much 
more  favorable  than  elsewhere  for  the  transmission  of  infec- 
tion.   Yet  in  the  home  the  chance  of  such  extension  of  disease 


154         THE  SOURCES  AND  MODES  OF  INFECTION 

is  not  as  great  as  has  been  supposed.  In  Providence/  the 
chance  of  persons  contracting  diphtheria  from  another  mem- 
ber of  the  family  who  has  the  disease  is  only  about  1  in  15. 
The  chance  of  a  child  between  two  and  six  years  contract- 
ing it  is  1  in  5;  of  an  adult,  1  in  40.  The  chance  of  a  woman 
contracting  the  disease  in  the  family  is  about  three  times  as 
great  as  that  of  a  man.  For  scarlet  fever  the  figures  are 
not  very  different.  Every  one  must  have  noted  repeated 
instances  where  only  one  of  a  family  of  children  is  attacked 
by  scarlet  fever  or  diphtheria,  the  rest  of  the  family  remaining 
well,  though  isolation  may  have  been  far  from  satisfactory. 
Danger  Less  outside  Family.  —  Outside  of  the  family,  in 
school,  in  factory  and  in  ordinary  social  relations,  except  per- 
haps in  the  play  of  young  children,  the  chance  of  transmitting 
the  disease  must  be  very  much  less.  Instances  are  not  rare 
where  children,  presumably  in  the  infectious  stage  of  scarlet 
fever,  have  mingled  freely  with  others  for  many  days,  or 
perhaps  weeks,  with  little  or  no  extension  of  the  disease.  I 
have  notes  of  an  instance  where  a  boy  with  scarlet  fever  in 
the  sore-throat  stage  attended  a  Sunday-school  festival,  and 
no  other  case  developed  among  the  large  number  of  children 
present.  At  an  infant  asylum  a  child  was  sick  with  mild 
scarlet  fever  for  17  days,  mingling  freely  with  about  75  chil- 
dren, mostly  under  5  years  of  age,  and  only  3  other  cases  re- 
sulted. At  a  large  school  a  girl  returned  at  the  end  of  the 
first  week  of  an  attack  of  scarlet  fever,  and  continued  her 
attendance  for  20  days.  Only  3  or  4  cases  developed  in  that 
school.  Similar  and  even  more  marked  instances  of  appar- 
ently feeble  infectivity  are  reported  by  others.  I  have  made 
no  attempt  to  collect  such  cases,  but  I  happen  to  have  before 
me  three  reported  by  Butler."  One  child,  taken  sick  Novem- 
ber 5,  attended  school  from  November  11  to  November  19. 
Two  other  children,  attacked  December  2G  and  27  respec- 
tively, attended  different  schools  up  to  January  16.     In  only 

'   Rep.  Supt.  of  Health,  Providonco,  1909. 

»  liutler,  Proc.  Roy.  Soc.  Mod.,  Lond.,  190S,  I,  Epidemiol.  Sec,  225. 


LIMITATIONS   TO  THE  VALUE  OF  ISOLATION      155 

one  of  the  three  schools  did  even  a  single  case  occur.  I  have 
known  of  a  teacher  with  virulent  diphtheria  bacilli  in  her 
throat  from  the  first  of  January  to  the  middle  of  April,  who 
taught  in  a  kindergarten  all  that  time,  but  who  did  not  trans- 
mit the  disease  to  any  one.  Many  of  the  instances  of  typhoid 
carriers  which  have  been  referred  to,  show  that  such  persons 
may  for  long  periods  of  time  fail  to  infect  any  one,  even  though 
employed  as  cooks  or  handlers  of  milk.  I  have  known  of 
cases  of  smallpox  remaining  for  several  days  in  lodging 
houses  or  hospital  wards,  or  traveling  on  railroads,  without 
any  one  contracting  the  disease.  Failure  to  infect  may  be 
due  sometimes,  perhaps,  to  intermittency  in  the  excretion  of 
germs,  sometimes  to  lack  of  contact,  and  sometimes  to  lack 
of  susceptibility  on  the  part  of  the  receiver  of  the  infection. 
Whatever  the  cause  may  be,  we  must  recognize  that  an 
infected  person  often  mingles  freely  with  the  public  without 
transmitting  the  infection  to  another. 

Carriers  less  Infective  than  the  Sick.  —  As  has  been 
stated,  it  is  not  improbable  that  the  infectivity  of  a  well  car- 
rier may  for  several  reasons  be  less  than  that  of  a  person  sick 
with  the  disease.  It  may  then  be  argued  that  the  danger 
from  carriers  has  in  the  preceding  pages  been  very  much 
exaggerated.  It  is  not  to  be  denied  that  the  probable  danger 
from  a  single  carrier  is  small.  Their  number,  however,  is 
large,  so  that  the  danger  from  all  carriers  is  large,  and  is, 
I  believe,  a  very  considerable  factor  in  the  maintenance  of 
the  contagious  diseases. 

Isolation  should  Vary.  —  In  applying  isolation  to  the 
prevention  of  disease  it  must  be  kept  in  mind  that  different 
conditions  require  different  procedures.  Thus  when  an  ordi- 
nary contagious  disease  first  appears,  after  a  considerable 
absence,  in  a  small  community,  or  in  an  institution,  very 
rigorous  measures  of  isolation  are  usually  desirable,  as  expe- 
rience has  shown  that  very  often  an  outbreak  is  thus  effec- 
tively checked  in  its  beginning. 

Isolation  in  Villages.  —  The  efficacy  of  isolation  under  such 


156 


THE  SOURCES  AXD  MODES  OF  INFECTION 


circumstances  is  well  illustrated  by  the  history  of  outbreaks 
of  the  common  contagious  diseases  in  the  smaller  cities,  town- 
ships and  villages  of  Michigan.  The  data  given  in  the  annual 
reports  of  the  board  of  health  of  that  state  are  of  great  epi- 
demiological interest,  and  my  discussion  of  the  subject  on 
another  occasion  is  here  given.^ 

"  Only  those  places  are  considered  which  have  remained 
free  from  the  disease  for  at  least  sixty  days,  and  this  unfor- 
tunately is  never  true  of  a  city  of  any  considerable  size.  The 
outbreaks  reported  are  arranged  in  groups,  one  in  which  iso- 
lation and  disinfection  were  both  enforced,  one  in  which  they 
were  both  neglected,  and  one  in  which  the  reports  did  not 
state  with  sufficient  exactness  what  restrictive  measures  were 
carried  out.  The  following  is  a  summary  of  some  of  the 
tables  in  the  report : 


Number  of  Cases 
per  Outbreak. 

Number  of  Cases 
per  Outbreak. 

Restric- 
tive Meas- 
ures not 
Enforced. 

Restric- 
tive 
Meas- 
ures 
En- 
forced . 

Restric- 
tive Meas- 
ures not 
Enforced. 

Restric- 
tive 
Measures 
Enforced. 

Typhoid  fever,  10  years .  . 

Diphtheria,  14  years 

Scarlet  fever,  14  years.  .  .  . 

Measles,  11  years 

Smallpox 

5.82 
11.12 
11.95 
48.30 

3.13 
2.11 
2.32 
3.03 

1900 

6.72 

4.85 

10.43 

27.60 

32.00 

2.22 
1.71 
2.53 
4.67 
3.80 

Isolation  Effective.  —  "  Several  things  are  to  be  noted  in 
connection  with  these  figures.  In  the  first  place,  isolation 
and  disinfection  accomplish  very  nmch  in  preventing  the 
extension  of  all  these  diseases.  The  number  of  facts  is  so 
great,  the  outbreaks  of  each  disease  running  into  the  hun- 
dreds, and  the  difference  between  good  and  bad  sanitation  is 
so  manifest  in  each  one  of  the  years  for  each  one  of  the 

'  J.  Mass.  Ass.  Bds.  Health,  Bost.,  1904,  XIV,  226. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION      157 

diseases,  that  the  success  achieved  must  be  a  very  real  one. 
It  appears  certain  that  isolation  and  disinfection  as  practiced 
in  the  smaller  communities  of  Michigan  reduce  the  cases  of 
contagious  disease  in  round  numbers  from  forty-five  to  ninety- 
five  per  cent.  In  scarlet  fever,  diphtheria,  measles  and  small- 
pox, isolation  appears  from  the  reports,  as  one  would  expect, 
to  have  very  much  more  restrictive  effect  than  disinfection. 

"As  will  be  shown  later,  disinfection  probably  has  little 
influence  in  restricting  contagious  diseases,  but  in  view  of 
existing  ideas  and  practices  it  is  probable  that  isolation  and 
disinfection  were  not  so  distinctly  separable  as  is  indicated  by 
the  reports  of  the  local  health  officers.  One  of  the  things 
which  appeared  most  remarkable  to  the  writer  in  these  re- 
ports is  the  apparently  great  restriction  of  measles.  It  has 
certainly  been  the  experience  in  all  our  larger  cities  that 
restrictive  measures,  no  matter  how  energetic,  have  had  very 
little  effect  in  reducing  the  mortality  from  this  disease.  But 
in  the  smaller  communities  in  Michigan  it  appears  that  where 
isolation  and  disinfection  are  well  carried  out  there  is  nearly 
ninety-four  per  cent  less  cases  per  outbreak  than  where  pre- 
cautions are  neglected. 

Cause  of  Success.  —  "  But  if  one  examines  the  original 
returns  of  the  health  officers  it  appears  plain  why  such  good 
results  are  obtained.  If  the  first  case  of  the  disease  coming 
to  a  community  is  early  recognized  and  isolated  the  chances 
are  good  that  the  outbreak  will  be  at  once  checked.  The 
chances  that  such  a  case  will  be  so  recognized  in  a  village  are 
very  much  greater  than  in  a  city.  If,  however,  the  outbreak 
is  not  checked  at  its  very  outset,  the  chances  are,  even  in  the 
country,  that  its  extension  will  be  very  considerable.  As  a 
matter  of  fact,  a  great  many  of  the  first  cases  coming  to  small 
communities  are  promptly  recognized  and  isolated,  and  as  a 
result  an  outbreak  is  prevented.  It  is  because  outbreaks  are 
in  rural  communities  so  often  nipped  in  the  bud  that  the 
application  of  restrictive  measures  in  such  communities  makes 
such  a  good  showing.    What  is  true  of  measles  is  true  also 


158  THE  SOURCES  AND  MODES  OF  INFECTION 

of  other  diseases,  particularly  of  scarlet  fever  and  diphtheria. 
It  is  success  in  applying  restrictive  measures  to  the  first  case 
that  is  the  principal  cause  of  the  apparent  efficiency  of  these 
methods.  If  every  appearance  of  contagious  disease  in  these 
rural  communities  had  gained  some  headway  before  restric- 
tive measures  were  applied,  the  showing  would  not  be  nearly 
so  favorable.  In  fact,  in  the  large  cities  in  Michigan,  where 
these  diseases  are  always  epidemic,  restrictive  measures,  even 
of  a  very  rigorous  type,  have  not  enabled  the  health  officers 
to  '  stamp  them  out.'  Thus  in  Detroit  it  was  the  custom 
for  many  years  to  'quarantine'  absolutely  every  house 
where  there  was  scarlet  fever  or  diphtheria.  No  one  was 
allowed  to  go  out,  and  the  inspectors  visited  the  house  twice 
a  day  and  furnished  provisions  for  the  poor  at  an  expense 
of  thousands  of  dollars  annually.  Yet  these  diseases  were  no 
more  'stamped  out'  in  Detroit  than  they  have  been  in 
Chicago  or  other  cities  where  milder  methods  have  prevailed." 

Isolation  in  Common  Diseases.  —  When  measles,  diph- 
theria or  scarlet  fever  appears  in  a  town  or  institution  which 
has  for  some  time  been  free  from  the  disease,  the  patient  ought 
to  be  isolated  until  it  is  as  certain  as  medical  science  can 
determine  that  he  is  free  from  infection.  At  least  this  should 
be  attempted.  If  it  should  happen,  as  it  sometimes  does, 
that  the  diphtheria  patient  retains  virulent  bacilli  for  many 
months,  or  that  the  scarlet-fever  patient  has  a  discharging 
ear  for  a  similar  period,  isolation  will  probably  have  to  be 
abandoned.  But  isolation  is  worth  trying,  for  in  the  majority 
of  instances  safety  is  secured  in  a  few  weeks.  Contacts  also 
should  be  carefully  examined  and  isolated,  or  otherwise  re- 
stricted as  to  their  relations  with  the  community.  If  after 
a  reasonable  time  the  disease  is  "  stampetl  out  "  the  health 
officer  is  to  be  congratulated.  If  it  is  not  stamped  out  he 
may  well  temper  the  rigor  of  his  restrictive  measures. 

When  a  rare  disease,  as  plague,  lei)rosy,  or  cholera,  appears 
in  lOurope  or  North  America,  equally  stringent  measures 
should  be  employed.     At  present  smallpox  belongs  rather 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION        159 

to  this  class  of  rare  diseases,  and  strict  isolation  of  the  first 
case  and  careful  examination  and  supervision  of  contacts  is 
desirable  and  useful. 

^  Many  Carriers  make  Isolation  Useless.  —  The  effective- 
ness of  isolation,  and  the  consequent  reason  for  its  practice, 
varies  inversely  as  the  number  of  carriers  and  missed  cases. 
With  the  enormous  number  of  carriers  of  pneumococci,  it  is 
entirely  useless  to  enforce  isolation  of  cases  of  pneumonia. 
Influenza  belongs  to  the  same  class  as  pneumonia,  in  which 
compulsorj^  isolation  is  useless.  It  is  probable  also  that  noth- 
ing which  the  health  officer  can  do  in  the  way  of  isolation 
will  have  any  effect  on  the  extent  of  outbreaks  of  cerebro- 
spinal meningitis.  The  enforced  isolation  of  typhoid  fever, 
owing  to  the  number  of  carriers,  will  usually  prove  of  little 
value.  While  it  is  probable  that  there  are  few  carriers  of 
measles,  yet  the  long  prodromal  but  extremely  infectious 
stage  renders  inefTectual  measures  of  restriction.  If  isolation 
of  measles  is  attempted,  little  can  be  hoped  for  other  than  a 
slight  postponement  of  the  age  of  attack,  and  no  measures 
should  be  adopted  which  inflict  any  great  hardship.  No  one 
advocates  the  isolation,  in  the  ordinary  meaning  of  the  term, 
of  pulmonary  tuberculosis.  It  is  not  attempted  in  this 
disease  simply  because  infected  persons  are  so  numerous  that 
it  is  impossible.  If  tuberculosis  were  as  rare  as  leprosy,  strict 
isolation  would  be,  and  should  be,  demanded.  On  the  other 
hand,  there  are  so  few  carriers  of  smallpox  that,  even  with 
the  mild  type  of  the  disease  prevailing,  strict  isolation  is  often 
advisable. 

To  discover  the  proportion  of  carriers  to  recognized  cases, 
for  each  disease,  is  a  matter  of  the  greatest  practical  impor- 
tance. We  must  have  a  fairly  clear  idea  of  how  many  un- 
recognized human  foci  of  infection  there  are  before  we  can 
determine  upon  what  methods  of  isolation,  if  any,  are  likely 
to  prove  effective.  Yet  the  investigation  of  carriers  has 
received  comparatively  little  attention  at  the  hands  of 
bacteriologists. 


160         THE  SOURCES  AND  MODES  OF  INFECTION 

Value  of  Hospitals.  —  Hospitals  are  useful  for  protecting 
the  family,  for  checking  outbreaks  in  institutions,  for  receiv- 
ing cases  from  lodging  houses  and  hotels,  for  furnishing  better 
medical  service,  and  for  relieving  the  overworked  housewife 
in  the  families  of  the  poor.  It  is  an  unnecessary  expense 
to  provide  hospital  accommodations  for  all  cases  of  scarlet 
fever  and  diphtheria,  or  for  ninety  per  cent  or  even  eighty 
per  cent.  That  half  or  two-thirds  of  the  cases  of  these 
diseases  can,  for  all  practical  purposes,  be  equally  well  cared 
for  at  home,  is  not  unlikely. 

Home  Isolation.  —  In  home  isolation  of  scarlet  fever,  diph- 
theria and  measles,  the  patient  should,  for  the  benefit  of  the 
public,  be  kept  in  the  house.  It  does  not  seem  reasonable  to 
prolong  isolation  until  all  possible  chance  of  infection  has 
ceased.  Exactly  what  the  period  should  be  in  each  disease 
should  now  be  a  topic  for  renewed  discussion. 

Isolation  in  Providence.  —  In  Providence  at  present  the 
period  of  isolation  for  scarlet  fever  is  four  weeks  from  the 
beginning  of  the  case.  Up  to  1902  the  period  v/as  five  weeks. 
Since  the  reduction  in  the  period  of  isolation,  the  attack  rate 
has  been  about  33  per  100,000  living,  although  one  of  our 
largest  epidemic  waves  occurred  during  this  period,  and  regis- 
tration is  certainly  far  better  than  formerly.  From  1884  to 
1901  the  attack  rate  was  about  34  per  100,000.  In  diph- 
theria, isolation  is  maintained  for  ten  days  after  the  disap- 
pearance of  the  membrane.  The  decrease  in  the  prevalence 
of  the  disease  which  followed  the  adoption  of  less  rigorous 
isolation  has  been  previously  alluded  to. 

Family.  —  When  the  attempt  is  made  to  isolate  the  patient 
in  the  family  from  the  family,  in  order  to  protect  other  mem- 
bers, the  duration  of  isolation  may  well  be  left  to  the  dis- 
cretion of  the  family.  It  is  the  duty  of  the  health  officer 
to  explain  that  the  longer  the  separation  of  sick  from  well 
is  maintained,  the  more  likely  it  is  to  be  effective.  In  scarlet 
fever  there  is  no  means  of  determining  when  the  patient  is 
free  from  infection.     I  am  in  the  habit  of  recommending 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION       161 

separation  from  the  family  for  six  weeks,  perhaps  a  somewhat 
shorter  time  if  the  case  is  a  mild  one,  and  longer  if  there  is 
aural  or  nasal  discharge.  In  Providence,  scarlet-fever  cases 
are  usually  sent  home  from  the  hospital  in  four  or  five  weeks, 
if  free  from  nose  and  ear  discharge.  No  regard  need  be  paid 
to  desquamation,  as  the  experience  of  English  hospitals  has 
shown  that  no  danger  is  to  be  feared  from  that  source.^  It 
is  absurd  to  isolate  with  strictness  a  diphtheria  patient  from 
the  rest  of  the  family  unless  cultures  have  shown  that  the 
rest  of  the  family  are  free  from  the  bacilli.  If  such  home  iso- 
lation is  to  be  undertaken  at  all,  it  should  be  continued,  if 
possible,  until  two  or  three  successive  negative  cultures  have 
been  obtained. 

Hospital.  —  Diphtheria  cases  in  Providence  are  usually  in 
the  hospital  until  two,  three  or  four  successive  negative  cul- 
tures from  the  throat  have  been  secured,  the  greater  precau- 
tion being  taken  when  the  child  is  to  return  to  an  institution. 
Sometimes  the  patient  is  sent  out  while  still  harboring  bacilli. 
The  duration  of  isolation  of  the  living  cases  is  19.65  days, 
and  the  percentage  of  return  cases  has  been  1.9.  In  London  ^ 
the  period  of  detention  of  6866  cases  was  57.5  days,  and  the 
percentage  of  return  cases  was  1.2,  about  0.5  per  cent  less 
than  in  Providence,  although  the  period  of  detention  was 
almost  three  times  as  long.  The  duration  of  stay  in  the  Provi- 
dence hospital  for  scarlet  fever,  surviving  cases,  is  45.67  days, 
and  the  percentage  of  return  cases  is  3.4.  In  the  London 
hospitals  the  period  of  detention  is  64.9  days,^  and  the  per- 
centage of  return  cases,  1902-04,  was  3.22. 

1  Metropolitan  Asylums  Board  Report  on  Return  Cases  of  Scarlet 
Fever  and  Diphtheria,  1902-04,  6.  See  also  my  discussion  of  this  subject 
in  FiskeFund  Essay  LII,  published  by  R.  I.  Medical  Society,  Providence, 
1909. 

*  Metropolitan  Asylums  Board  Report  on  Return  Cases  of  Scarlet 
Fever  and  Diphtheria,  1901-02,  59,  62. 

'  Metropolitan  Asylums  Board  Report  on  Return  Cases  of  Scarlet 
Fever  and  Diphtheria,  1902-04,  5,  23. 


162         THE  SOURCES  AXD  MODES  OF  INFECTION 

School.  —  School  children  in  infected  families  should  be 
excluded  from  school  for  a  liberal  period,  for  this  works  little 
hardship,  and  the  state  should  make  special  effort  to  keep 
its  schools  free  from  disease.  Yet  school  exclusion  may  be, 
and  often  is,  carried  to  excess.  In  Providence  children  living 
in  a  family  where  there  is  scarlet  fever  are  excluded  from 
school  for  four  weeks  from  the  beginning  of  the  last  case. 
In  all  except  the  poorer  class  of  houses  children  living  in 
other  families  in  the  house  are  permitted  to  attend  school. 
In  diphtheria,  children  in  the  infected  family  are  not  allowed 
in  school  for  four  weeks,  provided  that  if  all  the  school  chil- 
dren in  the  family  yield  two  throat  and  nose  negative  cultures, 
they  may  attend  school  after  the  warning  sign  has  been 
removed  (which  is  ten  days  after  the  disappearance  of  the 
exudation).  Children  in  other  families  in  the  better  class  of 
houses  are  admitted  to  school  if  one  negative  culture  is  ob- 
tained from  throat  and  nose.  After  the  expiration  of  a  month, 
all  children  in  families  where  there  has  been  diphtheria  are 
usually  admitted  to  school  whether  or  not  they  are  carrying 
morphologically  typical  bacilli,  and  of  course  quite  a  number 
do  go  to  school  while  infected.  Doubtless  these  carriers  may 
at  times  infect  others  in  school,  but  even  if  two  negative  cul- 
tures were  required  before  readmission,  some  children  would 
probably  still  prove  infectious.  Alisolute  security  is  impos- 
sible, and  the  rule  should  be  so  framed  as  to  accomplish  a 
maximum  amount  of  good  with  a  minimum  amount  of  an- 
noyance. 

Wage  Earners.  —  There  is  little  reason  for  excluding  wage 
earners  from  their  work  except  in  a  few  occupations.  Most 
of  the  carriers  we  cannot  restrain,  and  therefore  why  penalize 
those  who  have  the  additional  misfortune  of  sickness  in  their 
families  ? 

The  most  dangerous  carriers  are  those  who  handle  milk; 
hence  milk  producers  and  dealers  living  in  infected  families 
should  be  excluded  from  work.  Judging  from  the  number 
of  reported  outbreaks,  the  danger  is  probably  greater  for 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION       163 

typhoid  fever  than  for  any  other  disease.  It  is  probably  wise 
to  regulate  the  occupation  of  all  typhoid  contacts  who 
handle  any  kind  of  food  that  is  eaten  raw.  Perhaps  the  same 
should  be  done  with  diphtheria  contacts.  Teachers  and 
nurses  may  very  properly  be  prevented  from  following  their 
usual  vocations  if  they  live  in  infected  families.  It  has  been 
my  custom  also  to  exclude  from  work  car  conductors,  post- 
men, barbers  and  department-store  clerks.  I  doubt,  however, 
whether  this  is  always  advisable.  I  am  very  sure  that 
laborers,  mill  operatives  and  office  clerks  need  not,  under 
ordinary  circumstances,  be  kept  from  their  business. 

Summary. — As  regards  the  employment  of  isolation  for 
the  prevention  of  the  spread  of  infectious  disease  we  may 
fairly  conclude: 

1.  The  danger  to  be  apprehended  from  a  single  infected 
person  is  much  less  than  has  been  supposed. 

2.  Isolation  is  of  far  less  value  than  was  believed  a  few 
years  ago. 

3.  The  fewer  the  infected  persons  in  any  community  or 
institution  the  more  likely  is  isolation  to  be  successful.  Iso- 
lation in  an  extensive  outbreak  rarely  accomplishes  much. 

4.  The  effectiveness  of  isolation  varies  inversely  as  the 
number  of  missed  cases  and  carriers. 

5.  Hospitalization  in  such  diseases  as  scarlet  fever  and 
diphtheria  cannot  be  expected  to  exterminate  them,  and  the 
majority  of  patients  can  be  as  well  cared  for  in  their  homes. 

6.  In  diphtheria,  scarlet  fever  and  measles  there  is  rarely, 
and  only  in  certain  occupations,  any  necessity  for  interfering 
with  the  freedom  of  the  wage  earners  of  the  family. 

7.  The  isolation  of  school  children  should  be  more  strict 
than  that  of  adults,  for  less  hardship  results,  and  there  is 
more  danger  in  the  mingling  of  children  than  in  the  inter- 
course of  adults. 


CHAPTER  IV. 

INFECTION  BY  CONTACT. 

Most  Obvious  Mode.  —  Contact  infection  is  the  most 
obvious  mode  of  transmission  of  the  infectious  diseases.  For 
the  sick  to  touch  the  well,  and  thus  infect  them,  seems  to  be 
the  most  natural  way  of  accounting  for  the  spread  of  these 
diseases.  If  contact  infection  can  explain  epidemiological 
phenomena,  there  is  no  occasion  for  assuming  the  growth  of 
pathogenic  germs  outside  of  the  body,  or  of  infection  by  fo- 
mites  or  infection  by  air,  or  any  other  similar  theory,  and 
no  such  theory  should  be  adopted  as  a  working  hypothesis 
unless  pretty  strong  evidence  can  be  brought  to  its  support. 

Venereal  Diseases.  —  Gonorrhea  and  syphilis  are  univer- 
sally believed  to  be  transmitted  exclusively  by  contact,  and 
almost  invariably  by  a  special  kind  of  contact.  This  idea  is 
so  firmly  fixed  in  the  minds  of  medical  men  and  the  laity, 
that  no  matter  how  many  cases  occur  which  it  is  impossible 
to  trace  to  their  source,  no  one  ever  suggests  that  these 
diseases  are  air-borne,  or  that  their  germs  maintain  a  sapro- 
phytic life.  No  matter  how  much  the  patient  may  protest, 
it  will  still  be  held  that  the  infection  is  due  to  contact,  and 
in  the  vast  majority  of  cases  to  contact  involved  in  the  sexual 
act.  Gonorrhea,  particularly,  is  believed  to  be  almost  never 
transmitted  except  by  the  most  direct  contact;  yet  there  is 
at  times  as  much  reason  for  assuming  that  the  gonococcus 
is  air-borne,  or  clings  to  the  walls  of  rooms  and  thence  infects 
their  occupants,  as  there  is  to  assume  the  same  for  scarlet 
fever.  Yet  so  firmly  are  we  held  by  tradition  that  if  any  of 
us  should  suggest  such  an  origin  for  gonorrhea  it  would  pro- 
voke only  a  smile,  while  such  sources  of  scarlet  fever  are 

accepted  as  well  established. 

164 


INFECTION  BY  CONTACT  165 

Gonorrhea  in  Babies'  Hospital.  —  The  spread  of  gonococ- 
cus  infection  in  institutions  for  children  is  very  suggestive  of 
the  ways  in  which  other  infections  are  transmitted. 
.  A  very  interesting  account  of  institutional  infection  is  given 
by  Holt.^  At  the  Babies'  Hospital  in  New  York,  from  1894 
to  1898  inclusive,  64  cases  of  gonococcus  vaginitis  were  admit- 
ted, and  16  cases  developed  in  the  hospital.  In  the  summer 
of  1899,  three  children  suffering  from  gonococcus  vaginitis 
were  inadvertently  admitted  to  the  country  branch  of  the 
hospital,  and  though  the  danger  was  realized,  and  every  effort 
was  made  to  prevent  the  extension  of  the  disease,  by  pro- 
viding separate  nurses  for  the  infected  cases,  by  washing  the 
napkins  separately,  and  boiling  and  disinfecting  them,  never- 
theless 15  girls  contracted  vaginitis.  In  1901  similar  trouble 
was  experienced,  and  notwithstanding  the  most  vigorous 
measures  of  isolation  and  napkin  disinfection,  22  cases  devel- 
oped in  the  one  cottage  to  which  the  three  original  cases 
were  admitted.  The  physicians  were  inclined  to  look  upon 
general  house  infection  as  the  only  explanation  of  the  origin 
of  the  cases.  In  November,  1902,  a  new  hospital  building 
was  occupied  for  the  first  time,  and  it  was  hoped  that  it  could 
be  kept  free  from  the  disease,  but  5  cases  were  unwittingly 
admitted  during  the  first  six  months,  and  29  cases  of  vagi- 
nitis and  8  of  gonococcus  arthritis  developed  in  the  institu- 
tion. During  the  year,  13  cases  were  admitted,  and  66  were 
contracted  in  the  hospital.  Although  the  infected  cases  were 
all  strictly  isolated,  on  two  occasions  a  child,  even  in  another 
part  of  the  hospital,  developed  \he  disease.  For  a  time 
napkins  were  discarded  and  pads  used,  which  could  be 
burned;  separate  thermometers,  baths  and  supplies  were 
required  for  each  child;  wash  cloths  were  burned,  and  tub 
baths  forbidden.  Bed  clothing  was  disinfected  with  the 
greatest  care.  There  was  thought  to  be  absolutely  no 
opportunity  for  direct  contact  between  child  and  child. 
When  diphtheria  or  scarlet  fever  persists  in  an  institution  in 

1  Holt,  N.  York  M.  J.  [etc.],  1905,  LXXXI,  521. 


166         THE  SOURCES  AXD  MODES  OF   INFECTION 

such  a  manner,  it  is  at  once  attributed  to  persistent  infection 
of  the  building  itself,  and  it  is  suggested  by  Holt  as  a  pos- 
sibility in  this  instance  also. 

Carried  by  Nurses.  —  But  the  gonococcus  is  an  excep- 
tionally frail  organism,  and  it  is  impossible  to  believe  that 
persistent  infection  of  a  building  or  its  contents  can  occur. 
Actually,  in  the  Babies'  Hospital,  it  was  found  that  the  nurse 
was  the  carrier  of  the  germs  from  child  to  child,  and  the  two 
cases  which  developed  in  distant  wards,  and  which  were  sup- 
posed to  be  perfectly  isolated  and  under  the  care  of  different 
nurses,  were  attended  by  the  same  night  nurse  who  looked 
after  the  infected  cases.  Finally,  when  the  strictest  disin- 
fection had  failed  to  check  the  disease,  it  was  at  last  con- 
trolled by  requiring  that  the  nurses  should  practice  a  strict 
medical  asepsis,  and  disinfect  the  hands  in  every  instance 
immediately  after  bathing  or  changing  the  napkins  of  each 
child.  Here  was  a  disease  which  continued  to  spread  after 
the  erratic  and  persistent  manner  of  scarlet  fever  and  diph- 
theria, and  which  was  shown  to  depend  exclusively  upon  con- 
tact infection.  Air-borne  infection  and  fomites  infection  can 
have  no  part  in  institutional  gonococcus  infections,  for  the 
gonococcus  dies  so  quickly  that  such  modes  of  transfer- 
ence are  impossible.  Yet  this  infection  is  most  persistent 
and  troublesome  in  many  institutions  for  the  care  of  young 
children. 

Contact  not  always  Direct.  —  Gonorrheal  infection  is  not 
only  quite  common  in  institutions,  but  it  is  often  found  in 
infants  and  young  children  in  their  homes.  It  is  believed 
to  result  usually  from  the  child  sleeping  with  its  parents,  or 
to  direct  contact  with  the  hands  of  the  mother  while  washing 
or  dressing  the  child.  I  have  also  known  of  cases  of  the  direct 
transfer  of  the  disease  on  instruments  in  a  physician's  office. 

It  has  thus  been  necessary  to  modify  our  conception  of 
the  mode  of  transmission  of  gonorrhea,  and  although  it  is 
still  conceived  of  as  due  exclusively  to  contact  infection,  it 
is  now  recognized  that  the  contact  need  not  always  be  direct 


INFECTION  BY  CONTACT  167 

between  the  sick  and  the  well,  but  some  infected  person  or 
thing  may  act  as  intermediary.  Yet  from  what  is  known  of 
the  weak  resistance  of  the  gonococcus,  the  interval  of  time 
must  be  brief.  The  term  contact  infection  as  now  employed 
means  just  that  kind  of  transference  of  rather  fresh  infecting 
material  from  one  to  another.  It  does  not  necessarily  imply 
actual  contact  between  sick  and  well,  but  it  does  imply  that 
there  are  no  long  intervals  of  time  in  which  the  infective 
materials  may  become  dry  and  inert.  The  transfer  of  gonor- 
rheal pus  from  child  to  child  on  a  syringe,  or  on  the  fingers 
of  the  nurse,  are  examples  of  contact  infection.  If  the  pillow 
used  by  an  infected  child  were  put  away  for  a  week  or  two, 
and  when  brought  out  caused  ophthalmia  in  the  infant  who 
used  it,  it  would  be  an  example  of  fomites  infection.  The 
distinction  between  the  two  types  of  disease  transference, 
though  not  sharply  or  accurately  defined,  is  a  reasonable  and 
practical  one.  Thus  every  one  admits  that  gonorrhea  is  fre- 
quently transferred  by  indirect  contact  infection,  as  it  may 
be  called,  but  it  is  never  suggested  that  this  disease  is  spread 
by  fomites. 

Syphilis  spread  solely  by  Contact.  —  While  it  appears  to 
be  pretty  well  determined  that  Treponema  pallida  is  the 
cause  of  syphilis,  we  have  as  yet  no  data  as  to  the  cultivation 
of  this  organism  or  its  persistence  outside  of  the  body.  Its 
cultivation  outside  the  body  certainly  is  not  easy,  and  it  may 
be  suspected  that  its  life  is  short;  but  it  is  not  impossible 
that  the  virus  may  retain  its  virulence  for  some  days  or  weeks, 
as  does  that  of  rabies,  variola  and  vaccinia.  At  present  we 
have  to  rely  solely  on  clinical  evidence  as  to  these  points,  and 
the  universal  opinion  of  this  much  studied  disease  is  that 
the  virus  develops  only  in  human  beings  (and  some  of  the 
apes),  that  it  is  not  very  persistent,  and  that  it  is  trans- 
mitted solely  by  contact.  No  one  has  ever  suggested  that 
syphilis  is  an  air-borne  disease  in  the  ordinary  sense,  though 
one  or  two  cases  of  droplet  infection  have  been  reported.^ 
1  Buckley,  Syphilis  in  the  Innocent,  N.  Y.,  1894,  176. 


168        THE  SOURCES  AND  MODES  OF  INFECTION 

No  matter  how  obscure  may  be  the  origin  of  cases,  no  one 
would  attribute  them  to  aerial  infection,  or  to  dwelling  in  an 
infected  house.  Infection  during  the  sexual  act  is  undoubt- 
edly the  cause  of  by  far  the  larger  proportion  of  the  cases  of 
this  disease,  yet  in  the  aggregate  a  great  number  of  cases 
are  caused  in  other  ways. 

Non-sexual  Contact.  —  Buckley  in  the  work  just  quoted 
shows  that  probably  ten  per  cent  of  the  initial  lesions  are 
extragenital.  Exceedingly  infectious  lesions  at  times  are 
found  in  the  mouth  so  that  kissing  is  a  not  unusual  mode 
of  infection.  At  a  party  in  Philadelphia,  where  there 
were  kissing  games,  8  persons  were  infected  by  a  young 
man.  One  of  these  was  a  man  who  received  his  infection 
indirectly  on  the  lips  of  a  girl  just  previously  kissed  by  the 
syphilitic.^  Syphilis  is  often  transmitted  by  nursing  and 
the  sucking  of  wounds.  Mediate  contact  by  all  sorts  of 
infected  articles  is  common  and  Buckley  has  collected  many 
hundreds  of  instances.  Among  the  articles  njimed  are 
cups,  glasses,  spoons  and  other  eating-utensils,  pipes,  toilet 
articles,  underclothing,  bathing  suits,  handkerchiefs,  bed- 
ding, pins,  string,  wind  instruments  of  all  kinds,  glass 
blowers'  tubes,  pencils,  coins,  nursing-bottles,  sponges, 
syringes,  surgeons'  instruments,  dentists'  tools  and  barbers' 
utensils.  Buckley's  book  is  mainly  taken  up  with  an 
enumeration  of  these  modes  of  infection.  A  perusal  of 
these  reports  is  extremely  interesting,  for  though  it  is  not 
claimed  that  every  case  narrated  was  caused  in  the  man- 
ner assumed,  yet  it  is  evident  that  all  such  modes  of  trans- 
mission are  possible,  and  one  is  greatly  impressed  by  the  vast 
number  of  ways  in  which  fresh  secretions  may  be  passed  from 
one  to  another.  While  the  time  during  which  the  various 
articles  retained  their  infection  is  unknown,  or  at  least  is  not 
given  in  the  reports  of  cases,  it  is  apparent  that  almost  none 
of  the  instances  of  mediate  contact  were  the  result  of  long 
persistent  infection.  Fomites  infection  is  not  an  important 
»  ShambeiK,  J.  Am.  M.  Ahs.,  Chic:it!;o,  1<)11,  LVII,  783. 


INFECTION  BY  CONTACT  169 

factor  in  the  spread  of  syphilis.  Buckley^  says  that  the 
danger  from  soiled  clothing,  rags,  or  second-hand  garments 
"  is  infinitely  less  than  is  commonly  supposed,  and  relatively 
few  instances  have  been  recorded,  and  none  of  these  are  very 
clear  or  satisfactory."  In  the  few  instances  which  he  gives, 
the  infective  material  might  well  have  been  very  fresh. 

Typhoid  Fever  by  Contact.  —  Of  late  years  a  great  deal 
has  been  written  about  the  transmission  of  typhoid  fever  by 
contact  from  case  to  case,  and  this  mode  of  infection  appears 
to  have  attained  greater  prominence  in  connection  with  this 
than  with  any  other  of  the  common  infectious  diseases.  My 
attention  was  first  drawn  to  the  importance  of  contact  infec- 
tion in  typhoid  fever  by  the  vivid  description  given  by  Sedg- 
wick of  an  outbreak  which  he  investigated  in  1892  in 
Bondville, Massachusetts.  Hesays:^  "Children abound; and, 
as  there  are  no  fences,  and  because  it  is  the  custom,  they  mingle 
freely,  playing  together  and  passing  from  house  to  house. 
The  families  are  of  that  grade  in  which  food  always  stands 
upon  the  table;  meals  are  irregular  except  for  those  who  must 
obey  the  factory  bell.  The  children  play  awhile,  then  visit 
the  privies,  and  with  unwashed  hands  finger  the  food  upon 
the  table.  Then  they  eat  awhile  and  return  to  play.  Or, 
changing  the  order  of  things,  they  play  in  the  dirt  and  eat 
and  run  to  the  privy,  then  eat,  play,  and  eat  again,  and  this 
in  various  houses  and  in  various  privies.  For  them,  so  long 
as  they  are  friendly,  all  things  are  common,  —  dirt,  dinners 
and  privies;  and,  to  illustrate  exactly  how  secondary  infection 
may  go  on,  I  may  describe  in  detail  one  case  which  I  personally 
witnessed.  A  whole  family  (of  six  or  more)  was  in  one  room. 
Four  of  them  had  the  '  fever.'  Two  of  these  were  children 
in  the  prodromal  stage.  A  table  stood  by  the  window  covered 
with  food,  prominent  among  which  was  a  big  piece  of  cake. 
It  was  early  September,  and  a  very  warm  day;  but  every 
window  was  shut  and  the  odor  sickening.    Flies  innumerable 

^  Buckley,  Syphilis  in  the  Innocent,  New  York,  1894,  156. 
*  Sedgwick,  Rep.  Bd.  Health  Mass.,  Best.,  1892,  736. 


170         THE  SOURCES  AND  MODES  OF  INFECTION 

buzzed  about,  resting,  now  on  the  sick  people,  now  on  the 
food.  A  kind-hearted  neighbor  was  tending  the  baby.  By 
and  by  one  of  the  children  having  the  fever  withdrew  to  the 
privy,  probably  suffering  with  diarrhea,  but  soon  returning, 
slouched  over  to  the  food,  drove  away  some  of  the  flies,  and 
fingered  the  cake  listlessly,  finally  breaking  off  a  piece,  but 
not  eating  it.  Stirred  by  this  example,  another  child  slid 
from  his  seat  in  a  half-stupid  way,  moved  to  the  table,  and, 
taking  the  same  cake  in  both  hands,  bit  off  a  piece  and  swal- 
lowed it.  The  first  boy  had  not  washed  his  hands,  and  if 
the  second  boy  suffered  from  secondary  infection,  I  could  not 
wonder  at  it. 

"This  was  one  case;  but  I  have  seen  so  often  the  table  of 
food  standing  hours  long  in  the  kitchen,  and  serving  as  one 
station  in  the  dirty  round  of  lives  like  these,  that  it  is  easy 
for  me  to  understand  how  dirt,  diarrhea  and  dinner  too  often 
get  sadly  confused.  The  privies  had  been  obviously  in  bad 
condition,  and,  from  some,  filthy  streams  ran  down  between 
them  and  the  houses.  In  and  around  these  streams  the  chil- 
dren played.  Given  any  original  imported  case,  the  infection 
might  easily  have  reached  these  trickling  streams.  Children's 
fingers  might  thence  carry  the  germs  to  the  food,  and  thus 
the  journey  of  the  germs  from  one  living  intestine  to  another 
be  completed.  Or,  again,  given  in  such  a  community  an 
imported  case  and  no  disinfection,  as  was  the  condition  here 
at  first.  The  importer,  while  in  the  early  stages,  handles  with 
unclean  hands  food  for  others;  or  the  clothing  of  such  a  per- 
son gets  infected  and  is  handled;  there  need  be,  then,  no  diffi- 
culty in  completing  the  history.  It  follows  as  a  matter  of 
course." 

Contact  Typhoid  in  Spanish  War.  —  Probably  the  report 
of  Reed,  Vaughan  and  Shakespeare'  did  more  than  anything 
else  to  call  attention  to  tlie  importance  of  contact  infection 
in  the  epidemiology  of  this  disease.    This  commission  found 

'  Abst.  of  Rep.  on  the  Origin  and  Sproad  of  Typhoid  Fever  in  U.  S. 
Military  Camps  during  tlic  Spanish  War  of  1898,  Wash.,  1900. 


INFECTION  BY  CONTACT  171 

that  infected  water  played  little  part  in  the  development  of 
t3T)hoid  fever  in  the  camps.  They  also  found  that  probably 
every  regiment  brought  into  camp  one  or  more  mild  unrec- 
ognized cases  or  carriers,  and  that  these  were  the  starting 
points  of  outbreaks.  It  was  shown  that  the  fever  was  not 
evenly  distributed  through  the  regiments,  but  was  more  or 
less  localized  in  companies  or  squads  (p.  Ill  et  seq.). 

While  they  attributed  a  certain  amount  of  the  disease  to 
carriage  by  flies  and  by  dust,  they  considered  contact  infec- 
tion from  man  to  man  the  most  important  cause.  Of  1608 
cases  especially  studied,  and  which  were  accurately  located 
as  to  place  and  time,  35.01  per  cent  were  directly  connectible 
and  27.79  per  cent  indirectly  connectible  attacks;  total  con- 
nectible attacks,  62.80  per  cent  (p.  184).  Owing  to  the  unsat- 
isfactory methods,  or  lack  of  method,  of  excreta  disposal,  the^ 
shoes,  clothing  and  hands  of  the  men,  as  also  the  blankets 
and  tentage,  became  more  or  less  soiled  with  excreta,  and 
infection  of  the  men  became  easy,  and  in  fact  unavoidable. 
MeI^  detailed  as  hospital  orderlies  were,  after  they  had  per- 
formed the  duty  of  emptying  bedpans,  seen  to  go  directly 
to  their  meals  without  washing  their  hands,  and  even  to  dis- 
tribute food  to  their  comrades. 

In  South  Africa.  —  Similar  conclusions  were  arrived  at  by 
the  surgeons  who  studied  typhoid  fever,  which  proved  equally 
disastrous  to  the  English,  in  the  Boer  War,  but  on  the 
whole,  however,  the  English,  while  recognizing  the  impor- 
tance of  contact  infection,  did  not  place  so  much  stress 
upon  it  as  did  the  Americans.^ 

Contact  Typhoid  in  Civil  Life.  —  Outbreaks  in  civil  life 
have  of  late  frequently  been  attributed  largely  to  contact 
infection.  Winslow^  reported  an  outbreak  in  Newport,  R.  I., 
which  probably  had  its  origin  in  an  infected  well,  but  which 

1  Col.  Lane-Notter,  Tr.  Epidemiol.  Soc,  Lond.,  1904,  XXIII,  149; 
J.  Roy.  Army  Med.  Corps,  Lond.,  1905,  IV,  587,  693;  Tooth,  Brit.  M. 
J.,  Lond.,  1901,  I,  642. 

»  Winslow,  Technology  Quarterly,  1901,  XIV. 


172         THE  SOURCES  AND  MODES  OF  INFECTION 

was  continued  by  contact  infection.  He  coined  the  word 
"  prosedemic  "  to  describe  this  extension  of  the  disease  from 
case  to  case.  Water-borne  and  milk-borne  outbreaks  of 
typhoid  fever  usually  develop  suddenly,  a  large  number  of 
cases  being  reported  within  a  short  time.  That  they  do  not 
end  so  suddenly  but,  even  after  the  infected  water  and  milk 
are  eliminated,  continue,  decreasing  gradually,  is  a  phenome- 
non which  becomes  apparent  from  the  examination  of  the 
charts  of  such  outbreaks.  This  prolongation  of  the  outbreak 
is  due  to  the  prosedemic  infection  of  Winslow,  and  has  been 
noted  by  Whipple  ^  for  water  outbreaks,  and  by  Trask^  for 
milk  outbreaks.  During  a  water-borne  outbreak  at  Lincoln, 
England,  from  50  to  60  per  cent  of  the  cases  were  due  to 
personal  contact.^ 

Municipal  Outbreaks.  —  Many  local  outbreaks  have  been 
believed  to  be  due  almost,  if  not  quite,  exclusively  to  contact 
infection.  Such  an  outbreak  was  reported  by  Weston  and 
Tarbett  in  Knoxville,^  Jordan  in  Winnipeg,^  Magrath  in 
Springfield,"  Noetel  in  Beuthen,^  and  Weil  in  Rathsweiler.^ 
Freeman"  states  that  the  majority  of  the  outbreaks  in  the 
smaller  towns  of  Virginia  appear  to  be  due  to  contact  infec- 
tion. The  authority  of  Koch  has  done  much  to  direct  atten- 
tion to  the  importance  of  contact  infection  in  the  spread  of 
typhoid  fever  in  civil  life.  In  a  report  on  a  village  outbreak 
in  Trier  ^"  he  says  that  small  country  epidemics  will  usually 

'  Whipple,  Typhoid  Fever,  1908,  209. 

2  Trask,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Ilyg.  Lab.  Bull. 
No.  41,  38. 

3  Pub.  Health,  Lond.,  1905,  XVHI,  129. 

*  Weston  and  Tarbett,  Am.  Pub.  Health  Ass.  Rep.,  1907,  XXXIII, 
Pt.  1,  63. 

'  Jordan,  Abst.  in  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  563. 

«  Magrath,  Am.  J.  Pub.  Hyg.,  Post.,  1905,  I,  467. 

'  Noetel,  Ztschr.f.  Hyg.  u.Infectionskrankh.,Leipz.,  1904,  XLVII,211. 

*  Weil,  Med.  News,  N.  Y.,  1904,  LXXXIV,  467. 

»  Freeman,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  1263. 
'"  Koch,  Die  Bckiimpfung  dcs  Typhus,  Berlin,  1903. 


INFECTION  BY  CONTACT  173 

be  found  to  be  due  to  this  mode  of  infection.  In  the  particu- 
lar outbreak  investigated  all  the  cases  were  found  to  be  due 
to  contact,  that  is,  to  the  direct  transfer  from  person  to  per- 
son, and  the  source  was  in  most  instances  unrecognized  mild 
cases,  often  in  children.  He  then  describes  conditions  very- 
much  like  those  reported  by  Sedgwick.  Fecal  matter  was 
observed  in  the  dooryards  where  it  could  readily  infect  the 
children  playing  about,  and  would  certainly  be  carried  indoors 
on  their  shoes. 

Fulton,  1  Egbert  ^  and  others  have  shown  that  typhoid  fever 
prevails  far  more  extensively  in  the  country  than  in  the  city. 
Formerly,  when  less  was  known  about  the  etiology  of  the 
disease,  polluted  well  water  was  believed  to  be  the  chief  factor 
in  its  causation,  but  it  now  appears  that  it  is  far  more  likely 
to  depend  on  contact  infection. 

In  Hospitals.  —  Typhoid  fever  frequently  develops  in  hos- 
pitals and  other  institutions,  presumably  by  contact  infec- 
tion. Occasionally  explosive  outbreaks  due  to  infected  milk 
or  food  are  observed,  but  many  institutional  outbreaks  are 
characterized  by  a  slow  and  irregular  development  of  cases. 
The  disease  chiefly  attacks  those  who  are  brought  in  close 
contact  with  the  sick,  physicians  and  especially  nurses.  Fifty 
or  sixty  years  ago  few  cases  of  hospital  infection  were  re- 
corded. It  is  suggested  that  this  may  have  been  due  to  the 
fact  that  nurses  in  those  days  were  usually  women  well  along 
in  years,  and  therefore  not  so  susceptible  to  the  disease,  and 
usually,  perhaps  owing  to  the  greater  prevalence  of  the  dis- 
ease, immune.  During  recent  years  typhoid  fever  among 
nurses  and  ward  tenders  has  been  quite  common.  Joslin 
and  Overlander  ^  state  that  26  of  322  nurses  at  the  Mas- 
sachusetts General  Hospital,  and  12  of  94  ward  tenders,  con- 
tracted typhoid  fever  while  on  duty.  It  is  said  that  in  the 
London  hospitals  typhoid  fever  is  twenty  times  as  common 

'  Fulton,  J.  Am.  M.  Ass.,  Chicago,  1904,  XLII,  73. 
•      *  Egbert,  Am.  Med.,  Phila.,  1905,  IX,  649. 

»  Joslin  and  Overlander,.  Boston  M.  &  S.  J.,  1907,  CLVII,  428. 


174         THE  SOURCES  AND  MODES  OF  INFECTION 

among  nurses  as  among  women  of  the  same  ages  in  other 
occupations/  Goodall  ^  says  that  during  the  years  1892- 
1899  there  were  treated  in  the  London  hospitals  5913  typhoid 
patients,  and  100  attendants  contracted  the  disease.  In  four 
hospitals  not  admitting  typhoid  fever  no  cases  developed. 
Schuder,'  Neufeld,"  McCrae,^  Talayrach,"  EdsalF  and  others 
have  reported  an  excessive  prevalence  of  typhoid  fever  among 
the  attendants  on  cases  of  this  disease  in  hospitals,  and  they 
have  also  noticed  numerous  instances  in  which  it  has  devel- 
oped among  other  patients.  Nurses  and  others  infect  their 
hands  while  caring  for  typhoid  patients,  and  then  without 
washing  the  hands,  or  after  careless  washing,  infect  their 
own  mouths  directly,  or  by  handling  their  food  and  drink. 
Through  the  same  carelessness  they  also  infect  other  patients. 
Neufeld  refers  to  the  transfer  of  the  germs  on  a  thermometer 
and  in  a  bath.  Edsall  has  seen  a  nurse  given  the  double 
duty  of  emptying  the  bedpans  of  typhoid  cases  and  pre- 
paring special  diet,  and  a  patient  was  observed  to  empty  a 
bedpan  and  then  proceed  to  his  dinner  without  washing  his 
hands.  Nurses  also  wipe  out  the  mouths  of  patients  with  a 
bit  of  gauze  on  the  finger,  a  procedure  Avhich  was  believed  by 
Holt  to  be  one  of  the  means  of  spreading  gonorrheal  infec- 
tion in  the  Babies'  Hospital.  By  introducing  strict  cleanli- 
ness Edsall  was  able  to  stop  this  transference  of  the  disease. 
In  Other  Institutions.  —  Sometimes  quite  marked  out- 
breaks occur  in  institutions,  due  presumably  to  contact  in- 
fection. Usually  water,  milk  and  other  food  as  sources  of 
infection  can  be  excluded,  and  the  irregular  and  slow  devel- 
opment of  the  cases,  and  perhaps  the  discovery  of  carriers  or 

»  Pub.  Health,  Lond.,  1905,  XVIII,  142. 

>  Goodall,  Trans.  Epidera.  Soc,  Lond.,  1900. 

'  Schuder,  Ztschr.  f .  Ilyg.  u.  Infectionskrankh.,  Leipz.,  XXXVIII,  251. 

*  Neufeld,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1903,  II,  296. 
»  McCrae,  Mod.  Med.  [Osier],  Phila.  &  N.  Y.,  1907,  II,  82. 

•  Talayrach,  Arch.  d.  med.  et  de  pharrn.  milit..  Par.,  1903,  XLII,  393-. 
»  Edsall,  Am.  J.  M.  Sc,  Phila.,  1908,  n-s.,  CXXXV,  469. 


INFECTION  BY  CONTACT  175 

missed  cases,  renders  the  extension  of  the  disease  by  per- 
sonal contact  highly  probable.  In  an  almshouse  in  New 
Haven,^  37  cases  occurred  during  a  period  of  some  months. 
Mild  cases  were  concealed  and  worked  in  the  kitchen,  and 
it  was  impossible  to  teach  the  inmates  cleanly  habits.  At  a 
soldiers'  home  at  Lafayette,  Indiana,  there  were  65  cases 
due  to  contact  infection,  probably  chiefly  from  the  physician.^ 
At  the  State  Hospital  for  the  Insane  at  Trenton  there 
occurred  between  April  8  and  August  13,  1907,  80  cases 
with  16  deaths,  due  in  all  probability  to  contact  infection, 
largely  in  the  kitchen  and  pantry.^  Ravenel  *  reports  an 
outbreak  in  a  boarding  house  at  the  University  of  Wisconsin, 
where  41  cases  developed,  probably  as  the  result  of  a  patient 
working  in  the  pantry  during  the  prodromal  period  of  his 
illness.  Sedgwick^  reports  the  case  of  a  chambermaid,  and 
also  of  a  laundress,  who  contracted  typhoid  fever  from 
handling  soiled  linen.  A  waitress,  also,  who  ate  bread  cut 
by  the  other  two,  developed  the  disease.  Wolcott  tells  of 
the  matron  of  a  hospital  who  caught  the  disease  from  han- 
dling infected  bedding  and  neglecting  to  wash  the  hands. 
McCrae®  reports  an  instance  of  infection  from  careless  han- 
dling of  typhoid  cultures  in  the  laboratory,  and  a  similar 
case  occurred  in  an  insane  asylum  at  Northampton,  Mass.^ 
Dr.  Mann  tells  me  that  a  number  of  nurses  eating  at  the 
same  table  in  the  Homeopathic  Hospital  in  Boston  con- 
tracted typhoid  fever,  probably  from  a  waitress  whose  sister 
was  sick  with  the  disease,  and  who  herself  was  perhaps  a 
carrier. 

1  Rep.  Bd.  Health,  New  Haven,  190.5,  6. 

'  Hurty,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  1263. 

»  Rep.  St.  Bd.  Health,  New  Jersey,  1907,  149. 

*  Ravenel  and  Smith,  K.  W.,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII, 
1635. 

'  Sedgwick,  J.  Mass.  Ass.  Bds.  Health,  Bost.,  1900,  X,  148. 

*  McCrae,  Mod.  Med.  [Osier],  Phila.  &  N.  Y.,  1907,  II,  82. 
^  Rep.  Bd.  Health,  Mass.,  Bost.,  1899,  762. 


176        THE  SOURCES  AND  MODES  OF  INFECTION 

Contact  on  Shipboard.  —  Many  of  the  instances  of  infec- 
tion by  carriers  referred  to  in  Chapter  II  were  almost  cer- 
tainly the  result  of  contact  infection,  and  many  more  could 
be  easily  collected.  Occasionally  small  outbreaks  occur  on 
shipboard,  where  it  is  possible  to  exclude  all  modes  of  infec- 
tion but  contact.  Thus,  9  cases  on  an  Atlantic  liner  were 
traced  to  a  saloon  steward.^  On  the  United  States  ship  Con- 
necticut there  were  three  outbreaks  in  1907,  almost  certainly 
due  to  contact  infection.^ 

In  the  Fanuly.  —  During  1908  I  noted  three  small  out- 
breaks of  typhoid  fever  in  Providence,  due  apparently  to  con- 
tact infection.  In  one  instance  there  were  10  cases  in  three 
closely  related  families,  in  another  8  cases  in  three  such 
families,  and  in  the  third  outbreak  there  were  7  cases  in 
two  families.  Such  family  outbreaks  are  noticed  in  Provi- 
dence nearly  every  year,  and  they  are  referred  to  so  often 
in  current  medical  literature  that  it  does  not  seem  necessary 
to  give  additional  references.  Contact  outbreaks  in  hotels 
and  boarding  houses,  as  well  as  in  various  public  institutions, 
are  also  frequently  reported.  Hill  in  Birmingham,  in  1898, 
traced  10  per  cent  of  the  typhoid-fever  cases  to  contact  with 
other  cases.  In  Manchester  in  the  same  year  about  13  per 
cent  were  traced  in  the  same  way,  and  in  1906,  36.8  per  cent. 
Edsall  attributed  27  per  cent  of  250  cases  to  contact,  and 
Forster  117  of  386  cases,  and  McCrac  68  of  500  cases.  It 
would  be  easy  to  prolong  the  discussion  and  show  that  med- 
ical men  arc  everywhere  attributing  more  and  more  impor- 
tance to  contact  infection  in  this  disease.  It  is  to  be  noted 
that  in  few  of  the  reported  instances  of  contact  infection  is 
there  any  direct  and  conclusive  proof  that  the  disease  was 
caused  in  the  manner  alleged.  The  evidence  is  by  no  means 
so  convincing  as  to  mode  of  infection  as  it  is  in  so  many 
water-boriK!  and  milk-borne  outbreaks,  and  from  the  nature 
of  things  it  rarely  can  be  so. 

»  Rep.  Med.  Off.  Health,  Glasgow,  1907,  147. 

2  McDonnold,  Mil.  Surgeon,  C-arlisle,  Pu.,  1908,  XXIII,  29. 


INFECTION  BY  CONTACT  177 

Evidence  of  Contact  Infection.  —  But  when  water  and  food 
as  vehicles  of  infection  are  excluded,  when  the  disease  devel- 
ops in  persons  who  are  in  contact  with  the  sick  or  with  car- 
riers, and  when  the  fingers,  possibly  or  perhaps  evidently 
soiled  with  excreta,  are  seen  to  touch  food,  eating-utensils, 
and  sometimes  the  lips,  the  probability  of  the  development 
of  the  disease  in  this  manner  is  so  evident  that  observers 
are  constantly  seeing  in  contact  infection  the  cause  of  family, 
institutional  and  community  outbreaks  of  this  disease.  The 
importance  now  attributed  to  contact  infection  is  the  result 
of  a  careful  estimate  of  probabilities. 

Amount  of  Contact  Infection.  —  In  1908  there  were  11,375 
deaths  from  typhoid  fever  in  the  registration  area  of  the 
United  States,  which  doubtless  means  considerably  over 
100,000  cases.  The  registration  area  includes  about  one-half 
the  population  of  the  country.  While  a  certain  amount  of 
typhoid  fever  is  caused  by  milk,  it  must  be  a  very  small 
fraction  of  the  great  total.  As  will  be  shown,  milk  outbreaks 
are  usually  well  marked,  and  probably  not  a  very  great  deal 
of  milk-borne  infection  escapes  notice.  Again,  while  in  some 
cities  the  larger  part  of  the  typhoid  fever  is  due  to  infected 
water,  it  is  not  so  in  most  cities,  and  certainly  only  a  small 
part  of  the  total  typhoid  fever  in  the  country  can  be  traced 
to  such  a  source.  It  is  not  likely  in  my  own  city  for  instance 
that  more  than  20  per  cent  of  the  4300  cases  of  typhoid  fever 
during  the  past  twenty-five  years  have  been  due  to  infected 
water  or  milk;  and  infected  oysters,  celery,  etc.,  certainly 
play  a  very  unimportant  part  in  the  causation  of  the  disease. 
As  we  shall  see,  it  is  improbable  that  air-borne  infection 
or  dust  infection  is  of  any  moment  in  civil  life.  The  only 
other  important  source  of  typhoid  fever  which  has  been  sug- 
gested is  fly-borne  infection.  It  will  be  shown  also  that 
infection  by  means  of  flies  probably  accounts  for  only  a 
small  part  of  our  typhoid  fever.  By  exclusion,  then,  we 
are  led  to  the  conclusion  that  contact  infection  is  the  chief 
source  of  our  typhoid  fever. 


178         THE  SOURCES  AND  MODES  OF  INFECTION 

Why  should  we  not,  in  the  absence  of  direct  evidence  as 
to  other  modes  of  infection,  assume  at  once  that  contact, 
that  is,  the  more  or  less  direct  transfer  of  infective  material 
from  person  to  person,  is  the  principal  source  of  contagious 
disease  ?  Why  neglect  the  most  obvious  and  direct  mode 
of  transfer  in  favor  of  more  circuitous  paths  ?  There  are 
several  reasons  why  contact  infection  in  this  disease  has  been 
neglected. 

Why  Contact  Infection  has  been  Neglected.  —  One  reason 
lias  been  the  undue  emphasis  laid  upon  other  modes  of  trans- 
mission. Formerly  air  infection  was  considered  of  great 
moment,  and  as  this  fell  into  disrepute,  undue  weight  was 
attached  to  water  and  milk  infection,  partly,  no  doubt,  because 
of  the  dramatic  character  of  so  many  outbreaks.  Another 
reason  for  doubting  the  importance  of  contact  infection  is 
the  prevalent  notion  that  typhoid  fever  is  essentially  an  intes- 
tinal disease,  and  that  it  must  be  caused  by  infected  food. 
It  now  appears  that  typhoid  fever  is  not  an  intestinal  disease, 
and  in  some  cases  the  intestines  are  not  involved  and  the 
feces  are  free  from  bacilli  during  the  whole  sickness.  But 
the  bacilli  are  found  in  the  blood  stream  in  the  earliest  stages, 
and  it  seems  to  be  more  likely  that  they  enter  the  circulation 
through  the  upper  part  of  the  alimentary  tract  than  through 
the  intestines  after  running  the  gauntlet  of  the  gastric  secre- 
tions. Even  if  it  be  denied  that  the  tonsils  and  stomach  are 
the  portals  of  entry  of  the  typhoid  bacilli,  it  is  highly  probable 
that  bacilli  taken  into  the  mouth  in  small  masses  find  their 
way  to  the  lower  part  of  the  alimentary  tract  by  means  of 
the  small  quantities  of  saliva  which  are  constantly  swallowed. 
It  has  certainly  been  demonstrated  that  tubercle  bacilli  are 
swallowed  and  thus  reach  the  intestines. 

People  are  not  Cleanly.  —  Then,  too,  contact  infection 
in  tyj)hoid  fever  supposes  an  intimacy  with  the  most  offen- 
sive substances,  which  most  persons  would  vehemently  deny. 
Nevertheless  it  appears  that  tlie  fingers  of  human  beings, 
and  secondarily  everything  that  the  fingers  touch,  are  fre- 


INFECTION  BY  CONTACT  179 

quently  contaminated  with  excremental  matter.  The  colon 
bacillus  is  for  all  practical  purposes  a  good  test  for  the  pres- 
ence of  excrement,  and  it  is  somewhat  of  a  shock  to  learn  that 
it  is  found  on  the  hands  of  five  to  ten  per  cent  of  ordinarily 
cleanly  people.  Winslow  ^  and  Hall,^  while  studying  the  dis- 
semination of  typhoid  fever  by  carriers,  recovered  fecal 
bacteria  from  the  finger  nails  and  hands  after  the  usual  pro- 
cedures following  the  use  of  the  closet  and  toilet.  An  inspec- 
tion of  the  privies  or  water-closets  in  railway  stations, 
factories,  shops  and  tenement  houses  shows  that  they  usually 
present  evidence  of  contamination  with  feces  and  urine,  and 
in  many  instances  are  constantly  in  a  horribly  filthy  condition. 
It  is  only  in  the  better  class  of  hotels  and  residences  that  these 
apartments  are  kept  in  even  an  apparently  cleanly  condition, 
and  this  is  only  by  dint  of  constant  vigilance  and  frequent 
cleansing.  There  can  be  no  doubt  that  even  very  careful 
people  frequently  infect  the  seat,  their  fingers,  the  pull,  the 
door,  etc.,  and  that  in  a  large  proportion  of  privies  and  water- 
closets  the  users  almost  certainly  infect  their  fingers  with  at 
least  traces  of  their  own  or  others'  excremental  matter.  Yet 
how  many  persons  are  there  who  invariably  wash  the  hands 
after  the  use  of  a  closet  ?  How  many  make  it  a  rule  never 
to  put  the  fingers  in  the  mouth  ?  Yesterday  I  saw  a  workman 
carrying  a  can  of  beer  to  his  friends.  His  thumb  was  im- 
mersed a  couple  of  inches  in  the  beverage.  Had  he  washed 
his  hands  after  leaving  the  barroom  water-closet  ?  At  a 
recent  sanitary  convention  I  noticed  the  colored  waiter  stick 
his  finger  into  a  glass  which  he,  however,  did  not  remove,  and 
which  the  speaker  soon  drank  from.  What  was  the  recent 
history  of  that  finger  ?  Does  the  fruit  peddler  wash  his  hands 
after  using  the  tenement  privy  before  he  ventures  to  sort  his 
fruit  ?  Do  the  waitress,  the  milk  peddler,  the  candy  seller, 
the  Pullman  porter,  the  soda-water  clerk,  the  baker's  boy, 
the  delicatessen  man  always  wash  the  hands  before  taking 

1  Winslow,  J.  Mass.  Ass.  Bds.  Health,  Bost.,  1903,  XIII,  144. 

2  Hall,  Rep.  Med.  Off.  Health,  Bristol,  Eng..  1908,  27. 


180         THE  SOURCES  AXD  MODES  OF  INFECTION 

up  their  work?  Are  the  toilets  in  their  places  of  business 
so  cleanly  that  such  a  precaution  is  not  necessary  ?  How- 
ever shocking  it  may  seem,  it  is  certain  that  it  requires  only 
a  little  observation  to  demonstrate  that  the  path  from  intes- 
tines to  mouth  is  not  always  a  circuitous  one. 

Contact  with  Carriers.  —  Until  recently  it  would  have 
been  argued  that  contact  infection  is  not  an  important  factor 
in  typhoid  fever  because  only  a  small  proportion  of  the  cases 
can  be  shown  to  have  been  in  contact  with  this  disease,  and 
because  the  large  proportion  of  cases  of  this  fever  are  more 
or  less  isolated  in  their  homes  because  of  the  sickness.  But 
we  now  know  that  there  are  vast  numbers  of  mild  unrecog- 
nized cases,  and  most  important  of  all,  that  the  number  of 
carriers  is  very  great.  There  are  doubtless  200,000  cases  of 
this  disease  in  the  United  States  each  year.  If  only  3  per 
cent  of  these  become  chronic  carriers,  and  if  a  carrier  remains 
such  only  three  years,  we  should  have  a  carrier  population 
of  18,000  persons,  practically  all  unknown  and  taking  no  pre- 
cautions against  infecting  others.  If  we  add  to  these  the 
25  per  cent  of  convalescents,  who  for  some  weeks  are  excret- 
ing the  bacilli  in  their  urine,  it  appears  that  there  is  a  very 
respectable  army  of  unrecognized  sources  of  typhoid  infection. 

At  present  we  have  no  definite  knowledge  of  the  origin  of 
the  larger  number  of  our  cases  of  typhoid  fever.  In  view 
of  the  almost  universal  careless  habits  of  the  people,  and 
the  great  number  of  carriers,  why  not  adopt  as  a  working 
hypothesis  the  most  obvious  source  of  infection,  infection  by 
contact  ? 

Danger  from  Privies.  —  This  view  that  contact  infection 
is  the  most  important  factor  in  the  causation  of  this  disease, 
is  borne  out  by  the  observation  that  the  more  promptly  and 
effectively  human  excrement  is  disposed  of,  the  less  chance 
there  is  for  contact  infection  and  the  less  the  disease  prevails. 
When  the  disposal  is  exceptionally  bad.  as  in  army  camps, 
lumber,  mining  and  railroad  camps,  then  this  disease  is  al- 
most always  very  common.    In  thoroughly  sewered  and  clean 


INFECTION  BY  CONTACT  181 

cities,  provided  the  water  and  milk  are  not  contaminated, 
typhoid  fever  is  comparatively  rare.  The  privy  vault  stores 
up  fecal  matter  on  the  premises  and  is  rarely  kept  as  clean 
as  a  water-closet,  and  the  area  around  privies  is  often  filthy 
also.  It  has  often  been  noted  that  the  removal  of  privy 
vaults  has  been  followed  by  a  decrease  in  typhoid  fever.  In 
Providence  the  disease  fell  off  forty  per  cent  after  most  of  the 
privy  vaults  were  abolished.  Many  other  American  cities  in 
which  typhoid  fever  is  not  maintained  by  a  polluted  water 
supply,  show  a  steadily  decreasing  prevalence  of  this  disease 
as  privy  vaults  are  gotten  rid  of.  In  England  Pringle^  has 
shown  that  in  fourteen  towns  with  middens  the  typhoid  rate 
was  0.25  per  1000,  while  in  fourteen  water-closet  towns  it 
was  0.19.  In  Ipswich  there  was  a  marked  decrease  in  typhoid 
fever  following  the  removal  of  the  middens.^  A  similar  de- 
crease was  noted  in  Oldham,  Leicester^  and  other  cities.  On 
the  other  hand  more  "  pail  closets  "  remain  in  Nottingham 
than  in  most  English  cities,  and  to  this  Boobbyer^  attributes 
the  fact  that  typhoid  fever  has  decreased  less  in  that  town 
than  in  the  other  great  towns  of  England.  Like  reports  of 
a  decrease  in  the  disease  following  removal  of  privies  come 
from  such  widely  separated  places  as  Winnipeg  ^  and  Mel- 
bourne.® 

There  are  also  numerous  reports  to  the  effect  that  in  the 
same  town  typhoid  fever  is  much  more  common  in  houses 
without  water-closets  than  in  those  with  them.  This  may 
be  due  in  part  to  the  storing  of  fecal  matter  on  the  premises 
of  the  former,  and  it  may  be  due  also  to  the  fact  that  houses 
with  privies  are  usually  of  a  poorer  class,  and  the  inhabitants 
less  cleanly  in  their  personal  habits,  or  to  other  reasons;  but 

1  Pringle,  Pub.  Health,  Lond.,  1902-03,  XV,  630. 

2  Pub.  Health,  Lond.,  1908-09,  XXII,  414. 

3  Rep.  Med.  Off.  Health,  Leicester,  Eng.,  1908,  29. 
*  Boobbyer,  Rep.  Health  of  Nottingham,  1908,  53. 
'  Rep.  Dept.  Pub.  Health,  Winnipeg,  1908,  4. 

8  Jamieson,  J.,  Australas.  M.  Gaz.,  Sydney,  1903,  XXII,  56. 


182         THE  SOURCES  AND  MODES  OF  INFECTION 

these  facts  of  typhoid  distribution  accord  with  the  view  that 
the  disease  is  largely  spread  by  contact  from  person  to 
person.  In  Birmingham, ^  the  incidence  of  typhoid  fever  in 
"  pail "  and  water-closet  houses  was  as  65  to  43,  and  there 
has  been  a  steady  decrease  in  the  disease  as  the  "  pail 
closets"  have  been  abolished.  In  Nottingham  there  was  (in 
ten,  years)  1  case  in  each  37  houses  with  privies,  and  1  in 
each  558  water-closet  houses;  in  Salford  it  was  1  to  20  and 
1  to  42  respectively,^  and  in  Gorton  the  cases  were  two 
or  three  times  as  numerous  in  privy  houses  as  in  water- 
closet  houses.^  At  Leigh/  typhoid  fever  was  four  times 
as  prevalent  among  colliery  workers  as  among  the  rest  of  the 
population,  owing,  in  the  opinion  of  the  inspector,  to  the  filthy 
mode  of  excreta  disposal  in  the  mines.  In  Glasgow^  second- 
ary cases  of  the  disease  developed  in  23  per  cent  of  the  cases 
in  houses  with  privies  and  in  6  per  cent  of  the  cases  in  houses 
with  water-closets. 

Every  one  who  has  had  practical  experience  in  sanitary 
inspection  work  knows  that  privy  vaults  not  only  serve  as 
storehouses  for  excrement,  but  their  presence  encourages  its 
careless  disposal  in  the  yards  and  on  ash  heaps.  The  filthy 
condition  of  the  ground  about  the  houses,  leading  to  contami- 
nation of  feet  and  hands  of  children,  as  reported  by  Sedgwick 
and  by  Koch,  is  rarely  noticed  on  premises  provided  with 
water-closets.  It  may  be  urged  that  the  excess  of  typhoid 
fever  in  privy  towns  is  due  to  infection  by  flies  rather  than 
infection  by  contact,  and  this  may  be  true  to  some  extent; 
but  if  flies  were  the  chief  factor  we  should  scarcely  expect 
a  great  difference  between  water-closet  and  privy  houses  in 
the  same  town.     So  also  the  infection  of  miners,  as  noticed 

»  Rep.  Health  of  BirminKham,  1906,  49,  and  1908,  49. 
2  I'ringle,  Put).  Hcaltli,  Lond.,  1902-03,  XV,  6.30. 
'  Martin,  Pub.  Health,  Lond.,  1904-0.5,  XVH,    709. 
'  SweetinR.  Rep.  Med.  Off.  Lo<;al  (Jov.  Bd.,  Lond.,  1907-08,  XXXVII, 
.-57. 

'  Rep.  Med.  Off.  Health,  Glasgow,  1902,  97. 


INFECTION  BY  CONTACT  183 

by  Sweeting,  cannot  be  due  to  flies.  In  Providence  after  the 
removal  of  privies  the  decrease  in  tjq^hoid  fever  was  as  great 
in  winter,  when  there  were  no  flies,  as  during  the  fly  season. 

Amebic  Dysentery.  —  There  is  no  reason  why  amebic 
dysentery  may  not  be  transmitted  by  personal  contact,  but 
if,  as  is  generally  believed,  the  ameba  is  quite  widely  dis- 
tributed in  the  soil,  it  is  likely  that  in  countries  where  the 
disease  is  endemic,  man  is  the  least  common  source  of  infec- 
tion. Nevertheless  cases  do  develop  from  contact  with  other 
cases.  Lemoine^  has  reported  such  infections  in  France,  in 
one  instance  at  least,  probably  due  to  the  use  of  the  same 
bedpan,  douche,  etc.  The  infecting  case  was  a  carrier  of 
ten  years'  standing.  Allan  ^  writes  that  in  Charlotte,  N.  C, 
he  observed  four  cases  of  amebic  dysentery  which  he  believed 
were  due  to  contact  with  chronic  carriers. 

Bacillary  Dysentery.  —  Bacillary  dysentery,  like  typhoid 
fever,  is  a  great  scourge  of  military  life,  and  outbreaks  of  a 
serious  character  are  not  rare  in  institutions  such  as  hospitals 
for  the  insane.  The  bacillus  is  found  in  the  feces  of  the 
patients  and  also  in  convalescents.  There  is  every  reason 
for  believing  that  this  disease,  like  typhoid  fever,  is  frequently 
spread  by  more  or  less  direct  contact.^  Conradi  *  described 
a  village  outbreak  near  Metz  where  70  cases  occurred  during 
a  period  of  three  months.  Several  carriers  were  found  in 
infected  families,  and  conditions  favoring  contact  infection 
were  noted,  very  similar  to  those  observed  in  the  outbreaks 
of  typhoid  fever  studied  by  Koch  in  Trier.  Dodge  ^  reports 
the  case  of  a  laboratory  worker  who  got  some  of  a  culture 
of  the  dysentery  bacillus  in  his  eye;  the  tears  ran  profusely 
and  were  swallowed,  and  in  twenty-four  hours  an  attack  of 

1  Lemoine,  Bull,  et  mem.  Soc.  med.  de  hop.  de  Par.,  1908,  3  s.,  XXV, 
640. 

2  AUan,  Med.  Rec,  N.  Y.,  1910,  LXXVII,  63. 

3  Shiga,  Mod.  Med.  [Osier],  Phila.  &  N.  Y  1907,  II,  781;  Scheube, 
Diseases  of  Warm  CUmates,  2d  Ed.,  Phila.,  466. 

*  Festschrift  von  Robert  Koch,  1903,  555. 

'  Dodge,  Am.  Pub.  Health  Ass.  Rep.,  1905,  XXX,  310. 


184         THE  SOURCES  AXD  MODES  OF  INFECTION 

dysentery  developed.  An  outbreak  of  49  cases,  developing  in 
the  characteristic  slow  irregular  manner  of  contact  outbreaks, 
was  reported  in  the  Connecticut  Hospital  for  the  Insane.^ 
Kruse^  reports  a  similar  outbreak  in  Germany,  and  two  in 
Holland.  Epidemic  dysentery  is  quite  common  in  hospitals 
for  the  insane,  and  its  prevalence  is  explained  as  due  chiefly 
to  contact  infection,  for  the  carelessness  of  many  patients 
and  the  impossibility  of  controlling  their  habits  offer  every 
opportunity  for  this  sort  of  diffusion.^ 

Cholera  and  Contact.  —  If  typhoid  fever  and  dysentery 
are  spread  by  means  of  contact  infection,  we  should  expect 
that  cholera  would  be.  That  less  is  written  about  it  is  due 
probably  to  the  fact  that  in  recent  years  less  attention  has 
been  paid  to  cholera  than  to  the  more  common  diseases. 
The  literature  relating  to  typhoid  fever  has  of  late  been  many 
times  more  voluminous  than  that  relating  to  cholera.  Never- 
theless most  writers  attribute  some  importance  to  contact 
infection  in  this  disease,  and  some  consider  it  an  etiological 
factor  of  very  great  importance.  The  filthy  conditions  of  vil- 
lage life  described  by  Sedgwick  in  America  and  Koch  in  Ger- 
many as  giving  rise  to  typhoid  fever,  are  far  surpassed  in 
danger  by  the  habits  of  vast  numbers  of  the  poorer  people 
who  dwell  in  cholera-infested  countries.  The  opportunities 
for  the  direct  transference  of  fecal  matter  from  person  to 
person  are  far  greater  in  Asiatic  countries  than  they  are  with 
us,  and  a  number  of  writers  have  emphasized  the  part  played 
by  personal  contagion  in  this  disease.    Gotschlich  ^  refers  to 

»  Rep.  St.  Bd.  Health,  Connect.,  1903,  234. 

2  Kruse,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  370,  386. 

'  See  Reports  of  Comrnissionors  in  Jjunacy  (Eng.)  since  1903;  also 
Heuser,  Deutsche  nied.  Wclinschr.,  1909,  XXXV,  1G94;  Ryder,  Boston 
M.  &  S.  J.,  1909,  Cl.Xl,  681;  Ilaenisch,  Ztsclir.  f.  Hyg.  u.  Infections- 
krankh.,  Leipz.,  1908,  LX,  245;  Mott,  Tr.  Epidem.  Soc,  Lond., 
1901-02,  and  Arch.  Neurol.  Path.  Lab.,  Lond.  Co.  Asyl.,  Lond.,  1903, 
II,  735;  Prior,  Australas.  M.  Cong.  Tr.,  Victoria,  1909,  III,  383. 

*  Gotschlich,  Kolle  and  Wassermann,  Handbuch  [etc.],  Jena,  1904, 
IV,  108. 


INFECTION  BY  CONTACT  185 

this  factor,  and  a  number  of  our  officers  in  the  Philippines 
have  dwelt  upon  its  importance.  Woodruff  ^  says  that  while 
infected  water  played  some  part  in  the  great  epidemic  in 
Manila,  the  filthy  habits  of  the  people  were  the  chief  cause 
of  the  extension  of  the  disease.  He  speaks  of  an  outbreak 
of  eighty  cases  in  a  provincial  town  due  to  food  prepared  in 
Manila  by  a  caterer  who  soon  died  of  cholera.  Heiser  ^  con- 
siders that  the  handling  of  foodstuffs  and  of  the  leaves  in 
which  the  betel  nut  is  wrapped,  by  dealers  and  prospective 
purchasers,  is  one  of  the  chief  ways  in  which  cholera  is 
spread,  and  McLaughlin '  considers  the  "carrier"  with 
filthy  habits  the  greatest  source  of  danger.  He  says  that 
contact  infection  of  visitors  in  the  houses  of  the  sick  is  a 
common  means  of  disseminating  the  disease.  Schumburg  * 
reported  several  small  outbreaks  of  cholera  near  Hamburg 
caused  by  contact  infection.  Shakespeare  ^  reports  several 
instances  in  which  cholera  was  apparently  caused  by  han- 
dling soiled  linen,  some  of  which  might  perhaps  be  considered 
rather  as  examples  of  fomites  infection.  Macrae  ^  reports 
the  infection  of  hospital  nurses  with  cholera  in  a  manner 
similar  to  the  infection  of  nurses  with  typhoid  fever. 
Heiser  ^  says  that  in  the  Philippines,  physicians  and  nurses 
who  had  been  trained  to  aseptic  methods  did  not  contract 
cholera  but  untrained  attendants  frequently  did  through 
contact  with  patients. 

Diarrhea.  —  Newsholme  ^  believes  that  much  infantile 
diarrhea  is  due  to  direct  contact  infection  in  the  home,  and 
he  suggests  that  it  is  brought  about  by  "  sucking  infective 

1  Woodruff,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  1160. 

2  Heiser,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  856. 

3  McLaughhn,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1153. 

^  Schumburg,  Ztschr.  f.  arztl.  Fortbild.,  Jena,  1905,  II,  567. 
*  Shakespeare,  Rep.  on  Cholera  in  Europe  and  India,  U.  S.  Gov. 
Printing  Office,  1890,  81. 

«  Macrae,  Indian  M.  Gaz.,  1909,  XLIV,  361. 

^  Heiser,  Bull.  State  Bd.  Health,  N.  Y.,  Sept.,  1911. 

8  Newsholme,  J.  Hyg.,  Cambridge,  1906,  VI,  139. 


186       THE  SOURCES  AND  MODES  OF  INFECTION 

matter  from  dirty  fingers,  from  dummy  teats  and  in  other 
ways."  Naish  ^  and  Niven  ^  are  largely  in  accord  with  this 
view.  Sandilands,^  in  an  extended  article,  cites  others 
as  reporting  hospital  and  laboratory  infection  as  well  as 
evidence  from  house  and  neighborhood  outbreaks.  From 
his  own  study  of  multiple  cases  in  houses,  and  of  local  dis- 
tribution, he  is  convinced  that  contact  plays  an  important 
part  in  the  causation  of  this  disease.  Doubtless  the  most 
complete  epidemiological  study  of  summer  diarrhea  has 
been  made  by  Peters,*  and  it  should  be  read  by  every  one 
interested  in  the  subject.  Flies  are  considered  as  possible 
carriers  of  infection,  and  while  no  evidence  against  this 
theory  is  found,  much  positive  evidence  is  presented  to  show 
that  contact  infection  is  an  important  factor  in  the  causa- 
tion of  this  disease. 

Hook  Worm  Disease.  —  The  European  type  of  the  disease 
is  caused  by  Anchylostoma  duodenalis,  while  the  American 
type  is  due  to  a  slightly  different  species,  Uncinaria  ameri- 
cana}  The  symptoms  are  caused  by  the  growth  of  the 
worms,  which  are  about  half  an  inch  long,  in  the  intestine, 
where  they  fasten  themselves  to  the  intestinal  wall,  and 
not  only  suck  blood  themselves,  but  also  cause  considerable 
free  bleeding  from  the  wounds  which  they  make.  The 
eggs,  which  are  laid  in  the  intestine,  do  not  there  develop, 
owing  to  lack  of  oxygen,  but  hatch  soon  after  the  feces  are 
voided,  and  the  young  worms  then  pass  through  several 
stages  of  growth  in  moist  earth  or  mud. 

Until  recently  it  was  l)olievcd  that  human  infection  resulted 
from  drinking  water  containing  the  young  worms,  or  by  get- 

1  Naish,  Pub.  Health,  Lond.,  1909-10,  XXIII,  168. 

2  Niven,  Proc.  Roy.  Soc.  Med.,  Loud.,  1909-10,  III,  Epidemiol. 
Sect.,  131. 

'  Sandilands,  Proc.  Roy.  Soc.  Med.,  Lond.,  1909-10,  III,  Epidemiol. 
Sect.,  95. 

<  Peters,  J.  Hyg.,  Cambridge,  1910,  X,  602. 

'  Stiles,  U.  S.  Pub.  Ileallli  and  Mar.  IIosp.  Serv.  Hyg.  Lab.  BulL 
No.  10,  1903. 


INFECTION  BY  CONTACT  187 

ting  them  onto  fingers  or  into  food,  and  so  into  the  mouth. 
It  was  first  suggested  by  Looss  in  1898  that  infection  might 
take  place  through  the  skin,  and  he  believed  that  he  had 
himself  become  infected  in  that  way.  In  1901  he  proved  the 
correctness  of  his  surmises  by  experiments.  Later  Grassi, 
Fieri  and  Noe  placed  a  few  drops  of  water  containing  worms 
upon  the  skin,  but  only  one  of  the  three  became  infected. 
In  1902  Looss  successfully  repeated  his  experiments.  It  had 
meantime  been  noticed  by  Bentley  and  Boycott  and  Haldane 
that  dermatitis  was  apt  to  be  found  in  regions  where  the 
disease  prevailed,  and  it  was  suspected  that  it  might  be  due 
to  the  passage  of  the  worms  through  the  skin.  Smith  ^  showed 
that  by  placing  infected  earth  on  the  arm,  not  only  was  infec- 
tion caused,  but  there  resulted  a  dermatitis  at  the  site  of  the 
application.  Ashford,  whose  careful  study  of  the  disease 
in  Porto  Rico,  and  whose  brilliant  success  in  curing  its  vic- 
tims give  his  opinion  great  weight,  believes  that  the  skin 
is  by  far  the  most  important  avenue  by  which  the  worms 
infect  the  body.^  Uncinariasis  is,  then,  par  excellence,  a  dis- 
ease due  to  contact  infection. 

Fortunately  the  disease  is  usually  easily  curable  under 
medical  treatment,  and  the  freeing  of  individuals  from  worms 
by  this  treatment  is  necessarily  an  important  part  of  the 
prevention  of  the  disease.  It  is  evident  from  the  mode  of 
infection  that  the  pollution  of  the  soil  with  human  feces  is 
the  principal  factor  in  the  spread  of  the  disease.  Froperly 
constructed  privies  or  water-closets,  with  the  ultimate  dis- 
posal of  the  fecal  matter  by  deep  burial,  or  some  other  means 
to  prevent  the  pollution  of  the  upper  layers  of  the  soil,  are 
the  essentials  of  prophylaxis. 

Contact  Infection  less  Easy  in  Some  Diseases  than  in 
Others.  —  Gonorrhea  is  a  disease  in  which  the  infecting  secre- 
tion is  not  likely  to  be  much  handled,  and  when  it  occurs 

»  Smith,  C.  A.,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  1142. 
'  Ashford,    Rep.    of    Commission    on    Study    and    Treatment    of 
"Anemia"  in  Porto  Rico,  1904,  37. 


188  THE  SOURCES  AND  MODES  OF  INFECTION 

in  young  children  the  secretion  is  often  received  on  a  diaper. 
Yet  it  has  been  shown  in  the  preceding  pages  that  infantile 
gonorrhea  is  spread  exclusively  by  contact  infection.  Al- 
though the  children  themselves  take  little  part  in  the  spread 
of  the  disease  in  hospitals  where  they  are  isolated  from  one 
another,  and  although  nurses  and  physicians  have  been  shown 
the  danger  of  carrying  the  disease,  and  have  been  instructed 
to  take  the  greatest  precautions,  yet  this  disease  may  be 
maintained  for  months  in  an  institution  solely  by  means  of 
infection  borne  on  thermometers,  syringes,  etc.,  but  particu- 
larly on  the  hands  of  attendants. 

In  typhoid  fever  the  bacilli  are  contained  in  the  feces  and 
urine,  which  even  careless  people  are  supposed  to  avoid  touch- 
ing. Nevertheless  it  appears  that  the  fingers  of  careful  people, 
and  even  of  trained  nurses,  are  infected  in  this  manner,  and 
that  transfer  to  the  mouth  with  the  subsequent  development 
of  typhoid  fever  results.  There  is  much  evidence  that  this 
mode  of  transference  is  an  important,  if  not  the  most 
important,  factor  in  the  spread  of  this  disease. 

Contact  with  Saliva.  —  If  contact  infection  is  important 
in  such  diseases  as  gonorrhea,  typhoid  fever,  dysentery  and 
cholera,  in  which  the  infecting  material  is  not  constantly  at 
hand,  and  is  usually  strenuously  avoided,  how  much  more 
important  must  this  mode  of  transference  be  in  diseases  in 
which  the  specific  germs  arc  found  in  the  secretions  of  the 
nose  and  mouth  or  in  the  sputum. 

Danger  from  Fingers.  —  Probably  the  chief  vehicle  for 
the  conveyance  of  nasal  and  oral  secretion  from  one  to  another 
is  the  fingers.  If  one  takes  the  trouble  to  watch  for  a  short 
time  his  neighbors,  or  even  himself,  unless  he  has  been  par- 
ticularly trained  in  such  matters,  he  will  be  surprised  to  note 
the  number  of  times  that  the  fingers  go  to  the  mouth  and 
the  nose.  Not  only  is  the  saliva  made  use  of  for  a  great 
variety  of  purposes,  and  numberless  articles  are  for  one  reason 
or  another  placu'd  in  the  mouth,  but  for  no  reason  whatever, 
and  all  unconsciously,  the  fingers  are  with  great  frequency 


INFECTION  BY  CONTACT  189 

raised  to  the  lips  or  the  nose.  Who  can  doubt  that  if  the 
sahvary  glands  secreted  indigo  the  fingers  would  contin- 
ually be  stained  a  deep  blue,  and  who  can  doubt  that  if 
the  nasal  and  oral  secretions  contain  the  germs  of  disease 
these  germs  will  be  almost  as  constantly  found  upon  the 
fingers?  All  successful  commerce  is  reciprocal,  and  in  this 
universal  trade  in  human  saliva  the  fingers  not  only  bring 
foreign  secretions  to  the  mouth  of  their  owner,  but  there  ex- 
changing them  for  his  own,  distribute  the  latter  to  everything 
that  the  hand  touches.  This  happens  not  once  but  scores 
and  hundreds  of  times  during  the  day's  round  of  the  indi- 
vidual. The  cook  spreads  his  saliva  on  the  muffins  and  rolls, 
the  waitress  infects  the  glasses  and  spoons,  the  moistened 
fingers  of  the  peddler  arrange  his  fruit,  the  thumb  of  the  milk- 
man is  in  his  measure,  the  reader  moistens  the,  pages  of  his 
book,  the  conductor  his  transfer  tickets,  the  "  lady  "  the 
fingers  of  her  glove.  Every  one  is  busily  engaged  in  this  dis- 
tribution of  saliva,  so  that  the  end  of  each  day  finds  this 
secretion  freely  distributed  on  the  doors,  window  sills,  fur- 
niture and  playthings  in  the  home,  the  straps  of  trolley  cars, 
the  rails  and  counter  and  desks  of  shops  and  public  buildings, 
and  indeed  upon  everything  that  the  hands  of  man  touch. 
What  avails  it  if  the  pathogens  do  die  quickly?  A  fresh 
supply  is  furnished  each  day. 

Drinking  Cups.  —  Another  important  vehicle  of  transfer 
must  be  the  common  drinking  cup.  Davison^  estimated  that 
there  were  as  many  as  20,000  epithelial  cells  on  a  drinking 
glass  that  had  been  in  use  in  a  school  for  nine  days,  which 
well  illustrates  the  amount  of  infection  which  may  be  thus 
carried.  Cars,  steamboats,  hotels,  schools,  offices,  factories, 
theaters,  churches,  all  provide  a  common  vessel  from  which 
large  numbers  of  persons  drink,  thus  furnishing  an  almost 
ideal  method  by  which  perfectly  fresh  saliva  may  be  trans- 
ferred from  one  to  another.  Hundreds  of  thousands  of 
persons  must  be  each  day  in  this  manner  exchanging  the 

*   Davison,  Tech.  World  Mag.,  Chicago,  1908,  IX,  623. 


190         THE  SOURCES  AND  MODES  OF  INFECTION 

secretions  of  the  mouth.  When  travehng  in  the  steam  cars  I 
have  noted  the  shocked  expression  on  the  face  of  passengers 
as  a  fashionably  dressed  woman  was  seen  to  allow  her  pug 
dog  to  drink  from  the  common  glass,  —  not  a  pleasant  thing, 
of  course,  but  infinitely  less  dangerous  than  for  the  woman  to 
drink  from  it.  She  might  have  tuberculosis,  or  carry  diphthe- 
ria bacilli,  or  perhaps  even  have  mucous  patches  on  her  lips. 

Other  Kinds  of  Contact.  —  Besides  the  moistening  of  the 
fingers  with  saliva  and  the  use  of  the  common  drinking  cup, 
the  mouth  is  put  to  numberless  improper  uses  which  may 
result  in  the  spread  of  infection.  It  is  used  to  hold  pins, 
string,  pencils,  paper  and  money.  The  lips  are  used  to 
moisten  the  pencil,  to  point  the  thread  for  the  needle,  to  wet 
postage  stamps  and  envelopes.  Children  "swap"  apples, 
cake  and  lollipops,  while  men  exchange  their  pipes  and  women 
hatpins.  Sometimes  the  mother  is  seen  "cleansing"  the 
face  of  her  child  with  her  saliva-moistened  handkerchief, 
and  perhaps  the  visitor  is  shortly  after  invited  to  kiss  the 
little  one. 

Children  have  no  instinct  of  cleanliness,  and  their  faces, 
hands,  toys,  clothing  and  everything  that  they  touch  must 
of  necessity  be  continually  daubed  with  the  secretions  of  the 
nose  and  mouth.  It  is  well  known  that  between  the  ages  of 
two  and  eight  years  children  are  more  susceptible  to  scarlet 
fever,  diphtheria,  measles  and  whooping  cough  than  at  other 
ages,  and  it  may  be  that  one  reason  for  this  is  the  great 
opportunity  that  is  afforded  by  their  habits  at  these  ages 
for  the  transfer  of  the  secretions.  Infants  do  not  of  course 
mingle  freely  with  one  another,  and  older  children  do  not 
come  in  such  close  contact  in  their  play,  and  they  also  begin 
to  have  a  little  idea  of  cleanliness. 

Contact  Dangerous  because  of  Missed  Cases.  —  A  little 
observation  and  reflection  will  show  that  the  ways  are  num- 
berless in  which  fresh  secretion  of  nose  and  mouth  is  passed 
from  person  to  person.  Enough  has  been  written  to  demon- 
strate that  the  opportunities  for  contact  infection  arc  suffi- 


INFECTION  BY  CONTACT  191 

ciently  numerous  to  account  for  the  spread  of  the  contagious 
diseases  without  invoking  any  other  mechanism.  The 
chief  objection  to  this  view  is  that  while  it  is  true  that  there 
is  much  interchange  of  secretions,  it  is  between  well  per- 
sons, and  not  between  the  sick  and  the  well.  That  this 
objection  is  untenable  is  amply  demonstrated  by  the  evi- 
dence presented  in  Chapter  II.  There  can  no  longer  be  the 
slightest  doubt  that  there  are  large  numbers  of  mild  and  un- 
recognized cases  of  infectious  disease  mingling  freely  with 
the  public,  and  that  in  some  diseases,  and  perhaps  in  most, 
there  are  also  larger  numbers  of  perfectly  well  carriers  who 
also  are  unknown.  These  unrecognized  foci  are  clearly 
numerous  enough  to  cause,  by  their  contact  with  others,  the 
recognized  cases.  The  transfer  of  the  disease  by  fairly 
direct  means  is  so  obvious  and  easy  that  there  is  no  neces- 
sity for  invoking  the  agency  of  other  and  more  circuitous 
modes  of  dissemination.  Indeed  it  is  sometimes  said  that 
the  arguments  here  presented  prove  too  much,  and  that  if 
carriers  were  as  numerous,  and  contact  with  them  as  fre- 
quent, as  is  here  alleged,  none  could  escape.  But,  as  was 
stated  in  Chapter  II  and  on  page  153,  infection  does  not 
take  place  so  readily  as  is  generally  believed.  This  is 
demonstrated  clinically,  and  the  reasons  are  apparent. 
There  are  often  long  intervals  in  which  carriers  are  not 
eliminating  the  pathogenic  organism,  and  the  saliva  may 
not  contain  the  germs,  even  when  they  are  in  the  throat 
and  nose.  Germs  are  not  evenly  distributed  through 
saliva,  sputum  or  feces,  and  the  particle  transferred  may 
be  free  from  them.  The  infective  material  is  often  small  in 
amount  and  spread  in  a  thin  layer,  and  the  contained  organ- 
isms very  speedily  die.  Lastly,  small  numbers  of  pathogens 
are  often,  perhaps  usually,  destroyed  by  the  body.  We 
must  believe  that  usually  continued  or  somewhat  massive 
infection  is  necessary  to  cause  disease,  but  that  neverthe- 
less sometimes  a  single  infection  with  a  very  small  number 
of  germs  suffices.     The   number  of  unrecognized  foci  of 


192       THE  SOURCES  AND  MODES  OF  INFECTION 

infection  in  human  beings,  the  opportunities  for  contact 
infection,  and  the  natural  obstacles  to  successful  infection, 
appear  admirably  to  explain  many  otherwise  inexplicable 
phenomena  of  epidemiology. 

Bacteria  on  the  Hands.  — ■  Reference  has  already  been 
made  to  this  on  page  179.  Neumann,^  by  finding  fecal  bacilli 
on  water-closet  fixtures,  showed  how  the  hands  are  infected, 
and  he  also  showed  -  how  by  another  transfer  on  the  hands 
they  may  infect  bread,  rolls,  fruit,  butter  and  milk.  Colon 
bacilli  have  also  been  found  on  3  of  12  roller  towels.^  Pus- 
forming  organisms  have  their  natural  habitat  on  the  skin, 
and  the  work  of  the  surgeons  has  shown  the  tremendous 
importance  of  contact  infection,  which  they  have  now 
learned  most  successfully  to  avoid. 

Danger  from  the  Shuttle.  —  As  weavers  habitually  thread 
the  shuttle  by  sucking  the  yarn  through  the  eye,  mouth 
bacteria  may  in  this  way  be  transferred  from  one  to  another. 
This  has  been  alleged  as  a  mode  of  infection  in  tuberculosis, 
and  indeed  Brown'*  claims  to  have  traced  three  cases  to  this. 

Bacteria  on  Cups,  Pencils.  —  Vincenzi  found  diphtheria 
bacilli  in  the  holy  water  in  a  church  font.  Kinyoun"  found 
them  in  2  of  85  swabbings  from  the  woodwork  and  drink- 
ing glass  of  a  railway  car.  They  have  also  been  found  on 
glasses  and  cups  by  Albert  and  Boyd,'^  Perrow,^  and  in 
Chicago.^  Forbes,  in  Rochester,  found  thom  upon  a  drinking 
glass  which  was  believed  to  have  been  the  cause  of  an  out- 
break.    This  has  been  frequently  referred  to,  and  though  I 

1  Arch.  f.  Hyg.,  Munchen.  u.  Leipz.,  LIX,  174. 

2  Neumann,  Deutsche  med.  Wchnschr.,  Lcipz.u.Berl.,  1910,  XXXVI, 
2046. 

3  Bull.  Muss.  State  Bd.  Health,  Nov.,  1911. 

4  Brown,  Med.  Omcer,  1911,  IV,  27. 
'•  Vincenzi,  Seinaine  m6d.,  1S98. 

«  Kinyoun,  Med.  News,  N.  Y.,  1905,  LXXXVII,  193. 

'  Albert  and  Boyd,  Bull.  State  Bd.  Health,  la.,  Oct.-Dec,  1911,  37. 

*  Perrow,  Rep.  Health  Dcpt.,  Lynchburg,  Va.,  Sept.,  1911. 

»  Bull.  Dept.  Health,  Chicago,  April  22,  1911. 


INFECTIOX  BY  CONTACT  193 

have  not  been  able  to  find  Forbes'  original  article,  Dr.  Goler, 
the  present  health  officer  of  Rochester,  informs  me  that  the 
facts  are  as  reported.  Williams^  recovered  diphtheria  bacilli 
from  pencils  moistened  by  the  lips  of  children  sick  with  the 
disease.  The  observations  referred  to  in  the  chapter  on 
fomites  show  that  the  germs  of  this  disease  are  rarely  found 
on  fomites  and  then  only  on  objects  that  have  been  recently 
and  grossly  infected. 

Tubercle  Bacilli  in  Mouth.  — Not  only  are  tubercle  bacilli 
found  in  enormous  masses  in  the  true  sputum,  but  they 
are  often  present  in  the  saliva  as  well.  Neild  and  Dunkley^ 
found  them  in  saliva  from  the  tip  of  the  tongue  in  29  of  50 
cases  of  pulmonary  tuberculosis.  Park  found  them  in  the 
saliva  of  10  of  15  cases,^  and  refers  to  MoUer  recovering  them 
in  3  of  20  cases.  Le  Noir  and  Camus*  found  virulent 
tubercle  bacilli  in  the  nose  as  well  as  from  the  mouth  of 
tuberculous  cases. 

Pathogenic  Bacteria  on  the  Hands.  • —  With  the  present 
habits  of  human  beings  these  germs  must  be  constantly  trans- 
ferred to  the  fingers,  and  to  a  lesser  degree  to  everything  that 
the  fingers  touch.  Graziani''  found  tubercle  bacilli  on  the 
hands  of  4  of  8  tuberculous  patients,  and  on  3  of  them  3 
hours  after  washing  with  soap  and  water.  He  also  obtained 
the  bacilli  from  the  hands  of  4  out  of  6  non-tuberculous 
patients.  After  shaking  hands  with  tuberculous  patients  he 
was  able  several  times  to  recover  the  bacilli  from  his  own 
hands.  Baldwin''  found  bacilli  on  the  hands  of  patients  in 
the  Adirondack  Sanatorium.  They  did  not  use  handker- 
chiefs.   Of  10  patients  seen  in  private  practice  8  had  tubercle 

1  Williams,  Scientific  Bull.  2,  1895,  Health  Dept.,  N.  Y.  City,  14. 

^  Neild  and  Dunkley,  Lancet,  Lond.,  1909,  I,  1096. 

»  Park,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  157. 

*  Le  Noir  and  Camus,  Comp.  rend.  Soc.  de  biol..  Par.,  1908,  LXV,  464. 

*  Graziani,  Ann  d'  Ig.  Sper.,  XV,  709,  referred  to  by  Rosenau,  Sixth 
Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  28. 

«  Baldwin,  Tr.  Am.  Climat.  Ass.,  1898,  XIV,  202. 


194        THE  SOURCES  AND  MODES  OF  INFECTION 

bacilli  on  their  hands.  The  other  two  were  exceptionally 
careful.  Preisich  and  Schiitz  ^  found  tubercle  bacilli  on  the 
hands  of  children  in  a  children's  hospital  at  Budapest.  Of 
66  examinations  of  the  dirt  from  under  the  finger  nails  14 
were  positive  under  the  microscope,  but  owing  to  the  death 
of  the  animals  from  sepsis  their  virulence  was  not  demon- 
strated. Of  the  14  positive  cases,  11  had  tuberculosis,  or 
were  associated  with  it,  while  of  the  52  negative  cases  only 
5  were  associated  with  tuberculosis.  Dieudonne^  by  inocu- 
lation demonstrated  tubercle  bacilli  on  the  hands  of  2  of 
15  children.  In  this  connection  may  be  mentioned  the 
experiment  of  Schumburg,^  in  which  he  rubbed  an  ose  of  a 
culture  of  bacteria  on  his  hands,  and  recovered  the  germs 
after  15  and  16  handshakes.  Ostermann,^  on  the  other  hand, 
does  not  consider  contact  infection  of  much  importance  in 
tuberculosis.  While  he  recovered  tubercle  bacilli  from  the 
hands  of  7  of  14  phthisical  patients  and  from  1  attendant, 
he  obtained  them  only  4  times  from  42  children  living  in 
tuberculous  families  and  2  times  from  the  floors  occupied  by 
these  families.  He  does  not  find  that  bacteria  are  transferred 
from  hand  to  hand  as  readily  as  have  other  observers.  He 
also  made  a  few  cage  experiments  with  guinea  pigs  to  show 
that  infection  by  contact  is  less  effective  than  infection  by 
air. 

It  scarcely  needed  the  experiments  of  Annett  at  Liverpool  ^ 
and  Higgins"  at  Birmingham  to  show  that  virulent  tubercle 
bacilli  may  be  found  in  the  sputum  on  sidewalks,  or  those  of 
Dixon  ^  to  demonstrate  that  they  may  be  swept  up  on  the 
skirts  of  ladies'  dresses. 

1  Preisich  and  Schiitz,  Berl.  klin.  Wchii^chr.,  1902,  XXXIX,  466. 

2  Dieudonne,  Miinch.  mcd.  Wdinschr.,  1901,  XLVIII,  1439. 

3  Schuml)urg,  Ztschr.  f.  -irztl.  Forthild.,  Jena,  1905,  II,  567. 

*  Ostermann,  Ztsclir.  f .  Hyg.  u.  Infect  ionskrankh.,  Leipz.,  1908,  LX,  375. 
"  Annett,  Thompson  Yates   Laboratory  liep.,  1901-02,  IV,   Pt.  2, 
359. 

"  IliKgins,  Pul).  Iloaltli,  Lond.,  1909-1910,  XXIII,  100. 
'  Letter  from  Dr.  Samuel  A.  Dixon  to  author. 


INFECTION  BY  CONTACT  195 

In  Communion  Cups.  —  Anders^  found  tubercle  bacilli  in 
the  dregs  from  communion  cups  in  a  Philadelphia  church, 
and  Moller^  from  the  communion  cup  of  a  sanatorium 
chapel.  Davison^  found  them  on  a  glass  used  for  some 
weeks  in  a  high  school.  He  also  demonstrated  pneumococci. 
Klein ^  obtained  a  positive  tuberculous  reaction  once  after 
inoculation  of  the  swabbings  of  six  telephones,  although  on 
twelve  telephones  on  another  occasion^  he  was  unable  to 
find  either  diphtheria  or  tubercle  bacilli,  and  Rickards^  was 
unable  to  find  either  bacillus  on  twenty-four  mouthpieces 
of  lung-testing  machines  in  Boston.  Huhs^  found  tubercle 
bacilli  on  napkin  rings  in  the  sanatorium  at  Stadtwald,  but 
did  not  find  them  on  the  spirometer  which  was  in  daily  use. 
Price^  used  some  water  in  which  sanatorium  dishes  had  been 
washed  to  inoculate  eight  guinea  pigs,  all  of  which  died  of 
tuberculosis.  Washings  from  dishes  which  had  been  first 
washed  in  the  ordinary  way  showed  no  bacilli. 

Contact  Chief  Mode  of  Infection.  —  Since  it  is  true  that 
pathogenic  organisms  begin  to  die  or  lose  their  virulence 
when  thrown  off  from  the  body,  we  are  forced  to  conclude 
that  the  closer  the  relationship  in  time  and  space  with  the 
bearers  of  the  germs,  the  greater  the  chance  of  infection. 
Now  that  the  number  of  unknown  foci  of  infection  and  the 
opportunities  for  direct  transfer  of  secretions  have  been 
demonstrated,  the  deduction  is  certainly  permissible  that 
contact  infection  is  more  important  than  the  more  indirect 
infection  by  fomites  or  by  air. 

We  are  also  compelled  by  inductive  methods  to  place  the 
greatest  emphasis  upon  contact  infection.     In  the  chapter  on 

1  Anders,  J.  Am.  M.  .\ss.,  Chicago,  1897,  XXIX,  789. 

2  MoUer,  Deutsche  med.  Wchnsclir.,  1905,  XXXI,  548. 

3  Davison,  Tech.  World  Mag.,  Chicago,  1908,  IX,  623. 
*  Klein,  Lancet,  Lond.,  1908,  I,  1862. 

^  Ref.  J.  Am.  M.  Ass.,  1905,  XLIV,  1866. 

6  Rickards,  Rep.  Bd.  Heahh,  Boston,  1906,  91. 

7  Huhs,  Ztschr.  f.  Tuberk.  u.  Heilstattenw.,  Leipz.,  1906,  IX,  396. 

8  Price,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  167. 


196         THE  SOURCES  AND  MODES  OF  INFECTION 

infection  by  fomites,  and  particularly  in  that  on  infection  by 
air,  much  evidence  is  presented  to  show  that  infection  usually 
does  not  take  place  unless  contact  is  fairly  close.  The  views 
here  presented  as  to  the  great  importance  of  contact  infec- 
tion, and  the  comparatively  slight  importance  of  air  infection 
and  fomites  infection,  gradually  developed  after  considera- 
tion of  much  experimental  and  epidemiological  evidence. 
The  two  facts  which  more  than  all  others  have  contributed 
to  these  views  have  been  the  restriction  of  scarlet  fever  and 
diphtheria  to  single  families  in  the  same  house,  and  the  suc- 
cess of  certain  hospitals  in  preventing  cross  infection,  when 
contact  infection  is  strictly  guarded  against. 

Disease  Spreads  in  Dwellings  only  by  Contact.  —  The 
rarity  with  which  scarlet  fever  and  diphtheria  pass  from 
one  family  to  another  in  the  same  house  has  already  been 
alluded  to,  but  it  is  worth  considering  again.  Of  4306  other 
families  in  Providence  living  in  the  same  house  with  a  case 
of  scarlet  fever,  only  295,  or  6.8  per  cent,  were  later  invaded 
by  the  disease.  This  includes  all  families,  whether  careful 
or  careless,  and  whether  or  not  the  initial  case  was  removed 
to  the  hospital;  but  as  less  than  10  per  cent  of  the  cases 
have  been  removed  to  the  hospital  during  the  23  years 
covered  by  the  figures,  hospital  isolation  can  have  been  of 
little  moment.  This  amount  of  infection  is  surprisingly  small, 
and  of  itself  indicates  very  strongly  that  close  and  intimate 
contact  is  usually  necessary  for  the  extension  of  this  disease. 
A  further  study  of  the  facts  indicates  this  still  more  clearly. 
During  the  last  5  years,  scarlet  fever  has  extended  to  118 
of  1888  other  famihes,  or  6.3  per  cent.  In  54,  or  22  per  cent, 
of  the  cases  infection  occurred  during  the  first  two  weeks,  of 
which  37  were  during  the  first  week.  Most  of  these  cases 
during  the  first  two  weeks  probably  derived  their  infection 
from  the  first  family  Ijcfore  the  disease  was  recognized.  Only 
24  second  families  developed  their  infection  after  the  end  of 
the  second  week  and  while  the  warning  sign  was  on  the  house. 
This  is  the  time  when  the  patients  are  desquamating  and 


INFECTION  BY  CONTACT^  197 

when  the  disease  is  popularly  believed  to  be  most  infectious. 
These  24  cases  are  1.3  per  cent  of  the  1888  other  families  in 
the  infected  houses.  As  in  a  number  of  these  cases  there  was 
known  to  be  considerable  communication  between  the  fami- 
lies, it  seems  to  be  certain  that  in  an  ordinary  tenement 
house  scarlet  fever  is  not  readily  carried  from  one  family  to 
another,  and  that  effective  isolation  is  comparatively  easy. 
In  fact,  everything  goes  to  show  that  two  or  more  families 
may  live  in  the  same  house,  using  hallways,  doors,  and  even 
water-closets  in  common,  without  scarlet  fever  extending 
from  one  to  the  other.  All  that  is  necessary  is  that  there 
shall  be  absolutely  no  visiting  between  the  families,  and  that 
the  children  shall  never  meet  in  play.  I  do  not  know  that 
similar  data  have  been  collected  elsewhere,  but  Cameron^ 
has  shown  by  his  study  of  "return"  cases  of  this  disease 
that  in  many  instances  the  infecting  case  may  remain  in  the 
family  for  some  time,  providing  there  is  no  direct  contact 
with  the  well  persons. 

Diphtheria  is  as  little  likely  to  extend  from  family  to  family 
without  direct  contact  as  is  scarlet  fever.  During  the  last 
twenty-one  years,  in  Providence,  of  3667  other  families  living 
in  a  house  with  diphtheria,  only  263,  or  7.2  per  cent,  were 
invaded  by  the  disease.  During  the  five  years  1904  to  1908, 
of  1648  other  families,  114,  or  6.9  per  cent,  have  acquired  the 
disease.  Of  these,  only  38,  or  2.3  per  cent,  were  attacked  after 
the  first  week  of  the  initial  sickness  and  before  the  warning 
sign  was  removed.  As  was  sho"\vn  above,  many  of  these  infec- 
tions are  due  to  the  fact  that  the  first  case  is  not  recognized 
and  hence  the  different  families  in  the  house  continue  to  visit 
one  another;  or  in  some  instances  to  the  fact  that  persons  in 
the  second  family  carry  the  bacilli  for  a  time  without  being 
sick.  Probably  a  large  part  of  the  infections  during  the  first 
week  take  place  before  the  disease  is  recognized,  so  that  it 
seems  very  probable  that  less  than  2  and  perhaps  less  than 

1  Cameron,  Rep.  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria, 
Lond.,  1901-02,  98. 


198        THE  SOURCES  AND  MODES  OF  INFECTION 

1  per  cent  of  families  living  in  a  house  with  a  case  of  diph- 
theria contract  the  disease  while  the  warning  sign  is  on  the 
house.  I  have  given  particular  attention  to  the  cases  of  diph- 
theria arising  in  other  families  in  the  house  while  the  warning 
sign  remained  on  the  apartment  where  the  disease  first  ap- 
peared, and  almost  always  there  is  known  to  be  direct  inter- 
course between  the  families.  Contact  infection,  then,  seems 
to  be  necessary  for  the  transfer  of  diphtheria  from  one  family 
to  another  living  in  different  apartments  of  the  same  house. 

Disease  spreads  in  Hospitals  only  by  Contact.  —  Another 
strong  reason  for  this  view  that  contact  infection  is  the  chief 
mode  of  extension  for  the  common  contagious  diseases  is  the 
success  of  certain  hospitals  in  preventing  cross  infection  by 
minimizing  in  every  way  the  opportunities  for  infection  by 
contact.  The  Parisian  hospitals,  particularly  the  Pasteur 
Hospital,  have  been  leaders  in  demonstrating  the  success  of 
this  method.  In  most  hospitals  for  contagious  diseases  great 
effort  is  made  to  prevent  cross  infection  by  separating  the 
different  diseases  to  a  considerable  distance,  since  the  theory 
prevails  that  air-borne  infection  is  the  chief  mode  of  spread. 
This  view  so  dominates  hospital  practice  that  numberless 
ways  escape  notice  by  which  disease  is  spread  by  very  direct 
contact,  with  the  result  that  in  most  hospitals  cases  of  cross 
infection  are  continually  developing. 

French  Hospitals.  —  The  French  seem  to  have  been  the 
first  to  appreciate  the  importance  of  guarding  against  contact 
infection,  and  an  interesting  account  of  the  efforts  made  is 
given  by  Granchcr,^  who  was  one  of  the  pioneers.  Strict 
methods  of  "antisepsie  medicale,"  as  Grancher  calls  it,  were 
introduced,  and  it  was  found  possible  to  care  for  patients 
with  different  diseases  even  in  a  common  ward  with  far  less 
danger  of  transfer  than  before.  He  employed  wire  screens 
around  the  beds  to  impress  upon  the  nurses  the  necessity  for 
guarding  against  infection  by  contact.     During  the  years 

1  Grancher,  Cong.  Internat.  de  med.,  XIII.,  C.-r.  Par.,  1900,  Sec. 
de  mdd.  dc  I'enfancc,  478. 


INFECTION  BY  CONTACT  199 

1890  to  1900,  6541  patients  were  treated  in  Grancher's  wards, 
and  diphtheria  was  introduced  43  times,  but  only  once  did 
a  case  develop  in  the  wards.  Scarlet  fever  was  introduced 
19  times,  and  7  cases  developed  in  the  wards.  Less  suc- 
cess was  obtained  in  isolating  measles,  but  infections  were 
reduced  two-thirds.  Grancher  was  satisfied  that  even  this 
disease  was  spread  by  contact.  He  believed  that  in  clean 
wards  infection  is  rarely  air-borne;  it  is  "objective,"  not 
"  atmospheric."  In  several  other  French  hospitals  the  impor- 
tance of  preventing  contact  infection  has  been  realized.  In 
some  of  them  isolation  is  made  easier  by  placing  the  patients 
in  separate  rooms  or  cubicles;  in  some,  partitions  are  placed 
between  the  beds.  These  partitions  may  be  full  height,  or 
may  stop  short  of  the  floor,  and  reach  only  just  above  the 
head.  Sometimes  screens  only  are  used.  In  1897  the  Min- 
turn  Hospital  in  New  York,  a  small  private  hospital,  was 
built  to  provide  isolation  in  separate  rooms  for  cases  of  scarlet 
fever  and  diphtheria.  But  the  most  notable  example  of  the 
new  method  is  the  Pasteur  Hospital  in  Paris,  opened  in  1900. 
The  success  of  these  various  hospitals  in  preventing  cross 
infection  is  correlated,  not  with  the  amount  of  isolation  as 
ordinarily  understood,  but  with  the  care  with  which  aseptic 
measures  are  carried  out  by  the  attendants.  The  cubicles, 
partitions  and  screens  certainly  cannot  prevent  infection  if 
the  nurses  without  taking  proper  precautions  pass  from  one 
case  to  another.  This  is  shown  by  the  constant  development 
of  cross  infection  in  the  ordinary  hospital.  It  was  in  the 
Pasteur  Hospital  that  the  principles  of  medical  asepsis  were 
first  fully  appreciated  and  carried  out  in  a  practical  manner. 
The  hospital  consists  of  two  pavilions  with  about  fifty  beds 
each,  designed  ostensibly,  one  pavilion  for  scarlet  fever  and 
one  for  diphtheria;  but,  as  is  shown  below,  all  sorts  of  cases 
are  admitted.  For  the  care  of  all  these  "  other  diseases  " 
and  mixed  and  doubtful  cases,  twelve  single  rooms  are  pro- 
vided in  each  ward,  all  opening  into  a  common  corridor,  the 
doors  of  which  are  usually  left  open.    The  same  nurses  look 


200       THE  SOURCES  AND  MODES  OF  INFECTION 

after  different  diseases,  often  in  adjoining  rooms.  The  disci- 
pline of  the  hospital  attempts  to  secure  an  entire  avoidance 
of  contact  infection,  and  is  remarkably  successful.  Yet  the 
procedures  are  all  very  simple.  The  nurse  always  sterilizes 
her  hands  after  waiting  on  the  patient;  she  wears  a  gown, 
which  is  kept  in  the  room,  when  anything  is  done  which 
would  be  likely  to  infect  her  clothing.  Nothing  goes  into  the 
room  except  what  is  sterile,  and  nothing  comes  out  without 
being  at  once  sterilized.  To  train  nurses  sufficiently  to  take 
charge  of  a  ward,  two  years  are  necessary,  but  the  nurses 
whom  I  saw  there  were  carrying  out  these  details  with  the 
same  precision  and  unconsciousness  which  are  shown  by  the 
bacteriologist  in  his  laboratory. 

English  Hospitals.  —  The  principles  of  aseptic  nursing  as 
applied  to  contagious  diseases  have  been  employed  in  a  num- 
ber of  places  in  England,  as,  for  instance,  in  the  North 
Eastern,  South  Western  and  London  Fever  hospitals  in 
London,  at  Walthamstow  and  Manchester,  and  doubtless  in 
other  places.  The  methods  adopted  in  the  Monsall  Hospital 
at  Manchester,  and  described  by  Gordon,'  are  as  follows: 

"The  patient's  bed  in  the  general  ward  is  surrounded  with 
a  screen  covered  with  sheets,  which  are  kept  constantly  wet 
with  a  weak  solution  of  some  disinfectant.  The  main  pur- 
pose of  this  screen  is  to  serve  as  a  label,  and  to  remind  the 
nurses  that  certain  precautions  must  be  taken  for  the  patient 
behind  it.  At  the  same  time,  I  think  the  wet  sheets  may  pos- 
sibly arrest  infective  particles  that  are  projected  against  them 
in  the  acts  of  coughing  and  sneezing.  The  only  other  requi- 
sites are  two  glass  shelves  fixed  on  the  wall  behind  the  bed, 
and  a  locker  or  portable  cupboard  made  of  metal,  with  an 
enameled  surface,  which  can  easily  be  disinfected  and  kept 
clean. 

"  The  precautions  to  be  taken  by  the  nurses  in  attending 
patients  behind  this  screen  or  '  barrier '  are  printed  on  a 
card  fixed  to  the  screen,  and  are  as  follows: 

*  Gordon,  Rep.  on  Health  of  Manchester,  1908,  154 


INFECTION  BY  CONTACT  201 

Rules  in  Manchester.  —  "  Precautions  to  be  Observed  in 
the  Nursing  of  Barriered  Cases. 

"(l)  Rubber  gloves  are  to  be  worn  by  the  Nurse  for  all 
manipulations  connected  with  the  case,  including  the  han- 
dling of  clothes.  The  gloves  are  to  stand  in  a  bowl  of  1  in  400 
Izal  solution. 

"  (2)  The  following  utensils  are  to  be  marked  and  kept  on 
the  glass  shelves  or  in  the  locker  provided : 


To  be  kept  completely- 
immersed  in  a  1  to 
400  Izal  solution. 


Spatula 

Nozzles 

Clinical  Thermometer 

At  least  two  bowls. 

All  feeding  utensils  (plates,  spoons,  forks,  etc.). 

"(3)  A  plentiful  supply  of  wet  swabs,  with  a  bowl  contain- 
ing Izal  solution  to  receive  these  when  used,  is  to  be  kept  on 
the  locker.  Handkerchiefs  or  muslin  squares  are  not  to  be 
employed. 

"(4)  No  toys  or  books  that  have  once  been  used  inside 
the  barrier  are  to  be  taken  outside  it  except  to  be  destroyed. 

"  (5)  In  every  case  a  square  of  jaconette  is  to  be  placed  on 
the  pillow  slip,  and  over  this  a  piece  of  muslin ;  the  latter  is 
to  be  renewed  whenever  soiled. 

''(6)  An  overall  is  to  be  worn  by  the  Nurse  whenever 
either  the  patient  or  the  clothes  are  handled.  This  is  to  be 
kept  inside  the  barrier." 

The  success  of  the  methods  described  in  the  preceding 
pages  is  well  shown  by  the  published  figures.  At  the 
Pasteur  Hospital  from  October  1,  1900,  to  April  19,  1903, 
the  following  cases  were  received: 

Diphtheria 443         Scarlet  fever 92 

Sore  throat 166         Erysipelas 163 

Smallpox 524         Phlegmon  of  tonsil 20 

Chicken  pox 55         Other  diseases 219 

Measles 126  Mothers  with  infants. .  192 


202        THE  SOURCES  AND  MODES  OF  INFECTION 

Such  a  combination  furnishes  a  remarkably  fertile  field  for 
cross  infections.  During  the  next  year  about  750  cases  were 
admitted. 1 

During  this  whole  period  the  only  cases  which  developed 
in  the  hospital  were  5  of  smallpox,  2  of  erysipelas  and  1  of 
diphtheria.  Dr.  Loiseau  writes  me  that  since  1904  the  per- 
centage of  cross  infections  has  been  less  than  0.1  per  cent. 
At  the  Minturn  Hospital  in  New  York  there  has  been  no  in- 
stance of  infection  in  the  hospital.  At  the  Monsall  Hospital 
in  Manchester  in  1908  a  large  number  of  persons  admitted 
with  mistaken  diagnosis  were  cared  for  in  the  wards  by  the 
methods  described  Avithout  contracting  the  disease,  and  a 
number  of  cases  of  mixed  infection  were  cared  for  in  the  open 
wards  without  infecting  others,  except  in  one  instance  when, 
owing  to  a  mistake  in  orders,  "  barrier  "  isolation  was  not 
promptly  instituted.  A  letter  just  received  from  Dr.  Arnold, 
who  has  succeeded  Dr.  Gordon  at  Monsall,  states  that  in 
order  that  the  patient  may  see  and  be  seen,  and  to  avoid 
the  dampness  of  the  wet  sheet,  he  has  substituted  a  tape 
which  as  effectually  prevents  the  mythical  aerial  flight  of  the 
germs,  or,  to  speak  literally,  equally  well  reminds  the  nurse 
that  she  must  bo  clean. 

Is  Tuberculosis  Air-borne  ?  —  It  is  assumed  that  tuber- 
culosis, as  it  occurs  in  human  beings,  is  usually  an  air-borne 
disease,  and  as  will  be  shown  on  another  page,  there  is  more 
reason  for  such  an  assumption  concerning  this  than  concern- 
ing most  diseases.  Yet  there  is  in  certain  quarters  a  growing 
tendency  to  attribute  to  contact  infection  more  importance 
than  formerly.  Yet  it  must  be  confessed  that  most  writers 
on  this  disease  lay  no  emphasis  on  contact  infection,  and 
some  scarcely  mention  it.  Cornet,"^  in  speaking  of  kissing, 
the  most  direct  means 'of  contact  infection,  says  that  it  is 
incredible  that  tuberculosis  should  be  transmitted  in  this 
way,  for  the  saliva  is  ordinarily  germ  free,  and  the  germs  if 

1  Martin,  Bull,  med.,  Par.,  1904,  XVIII,  251. 

*  Cornet,  Nothnagcl's  Encyclopedia,  Tul)crculosis,  187. 


INFECTION  BY  CONTACT  203 

present  would  not  be  carried  to  the  lungs.  Cornet's  first 
contention  is  certainly  not  correct,  for  Neild  and  Dunkley,  as 
before  mentioned,  found  tubercle  bacilli  on  the  tip  of  the 
tongue  of  phthisical  patients  examined  during  intervals  of 
freedom  from  cough.  They  also  report  cases  of  lupus,  due  in 
all  probability  to  inoculation  with  saliva,  and  refer  to  others 
reported  by  Wild.^ 

There  has  been  little  experimental  work  to  determine  the 
part  played  by  contact  infection  in  tuberculosis.  The  work 
of  Bartel  and  Spieler'  indicates  that  guinea  pigs  exposed 
under  natural  conditions  to  contact  with  the  members  of  a 
tuberculous  family  more  often  develop  the  disease  than  do 
animals  exposed  merely  to  the  air  of  the  room,  while  the 
experiments  of  Packard,  though  inconclusive,  indicate  little 
difference. 

Infection  by  Alimentary  Tract.  —  There  seems  to  be  evi- 
dence that  the  tonsils  may  be  the  seat  of  infection  in  many 
cases  of  tuberculosis.  Harbitz^  has  verj'  forcibly  called  atten- 
tion to  the  probability  that  tubercle  bacilli  frequently  gain 
access  to  the  body  through  the  tonsils.  He  examined  the 
tonsils  and  lymphatic  glands  of  a  large  number  of  children, 
and  found  latent  tuberculosis  in  many  of  the  tonsils,  and 
latent  bacilli  in  the  cervical  glands  in  17  instances,  much  more 
often  than  in  the  mesenteric  glands.  He  thinks  that  a  more 
careful  study  of  the  tonsils  and  lymph  nodes  would  reveal 
much  latent  tuberculous  infection,  and  he  thinks  that  a  con- 
siderable amount  of  infection  takes  place  through  the  tonsils. 
Harbitz  mentions  Grawitz,*  Aufrecht^  and  Beckmann  as  sup- 
porting this  view.  Ravenel  and  Reichel  ^  review  much  litera- 
,ture,  and  refer  to  Wood's  experimental  infection  of  swine 

'  Wild,  Brit.  M.  J.,  1899,  II,  1353. 

^  Referred  to  in  the  chapter  on  infection  by  air. 

3  Harbitz,  J.  Infect.  Dis.,  Chicago,  1905,  II,  143,  and  especially  198. 

'  Grawitz,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  711. 

*  Aufrecht,  Verhandl.  d.  deutsch.  path.  Gesellsch.,  Bed.,  1901-02, 
IV,  65. 

*  Ravenel  and  Reichel,  J.  Med.  Research,  Best.,  1908,  XVIII,  1. 


204       THE  SOURCES  AND  MODES  OF  INFECTION 

through  the  tonsils,  the  course  of  the  bacilH  being  apparentty 
through  the  submaxillary  and  cervical  glands.  Benome  ^ 
caused  infection  in  animals  through  the  mouth  and  pharynx. 
Bandelier"  finds  primary  tuberculosis  of  the  tonsils  not  so  rare 
as  is  generally  believed,  but  he  does  not  consider  the  tonsils 
as  a  frequent  starting  point  of  phthisis.  Mohler  and  Ravenel 
from  experiments  and  observations  consider  the  mouth  as 
a  frequent  site  of  infection  in  the  tuberculosis  of  hogs. 

Contact  Infection  in  Tuberculosis.  —  The  nose  also  may 
be  the  seat  of  infection.  Cornet,^  by  applying  infective  ma- 
terial by  means  of  a  feather  to  the  nasal  mucous  membrane 
of  guinea  pigs,  was  able  to  produce  disease  of  the  nose  and 
submaxillary  glands.  Renshaw  *  was  able  in  the  same  way 
to  infect  seven  of  eight  animals.  As  tubercle  bacilli  are  nu- 
merous upon  the  hands  of  consumptives  and  upon  various 
articles  used  by  them,  it  is  evident  that  fresh  bacilli  must  be 
frequently  carried  to  the  mouth  and  nose  of  persons  near  by, 
and  may  either  infect  directly  through  the  mouth,  nose  and 
pharynx,  or  may  be  swallowed  and  enter  the  circulation 
through  the  lower  part  of  the  alimentary  canal.  The  only 
question  is,  How  frequently  does  this  happen?  As  was  stated 
above,  it  is  the  opinion  of  many  that  it  is  a  very  common 
mode  of  infection.  Moore  ^  is  of  the  opinion  that  in  cat- 
tle tuberculosis  is  spread  chiefly  by  the  animals  licking 
one  another,  and  by  their  eating  and  drinking  from  the 
same  vessels.  Bartel^  believes  that  infection  by  pharynx, 
stomach  and  intestines  is  more  common  than  has  been  sup- 
posed, in  which  view  he  supports  Weichselbaum,^  Volland,** 

'  Benome,  Ref.  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  888. 
'  Bandelier,  Beit.  z.  Klin.  d.  Tuberk.,  Wiirzb.,  1906,  VI,  1. 
•^  Cornet,  Nothnagcl's  Encyclopedia,  Tuberculosis,  154. 
^  Renshaw,  J.  Path,  and  Bacteriol.,  Lond.,  1901,  VII,  142. 
">  Moore,  Conference  of  Sanitary  Officials,  N.  Y.,  1907,  37. 
"  Bartol,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  95. 
'  Weichselbaum,   Festsch.  VI    Konf.    Internat.  Tuberk.,    Wien    u. 
Leipz.,  1907. 

*  Volland,  Bed.  klin.  Wchnschr.,  1899,  XXXVI,  1031. 


INFECTION  BY  CONTACT  205 

Kavacs'  and  Preisich  and  Schiitz.^  Among  others  who  at- 
tribute much  importance  to  contact  infection  may  be  men- 
tioned Wassermann,^  Calmette  and  Landouzy.* 

.  Certainly  the  opportunities  for  the  direct  transfer  of  fresh 
moist  infective  material  in  the  home  of  a  phthisical  patient 
must  be  very  great,  while  the  chance  of  the  infective  material 
becoming  dried,  pulverized  and,  while  still  virulent,  being  car- 
ried to  the  pulmonary  alveoli,  must  be  comparatively  small. 
Unless  there  is  some  good  reason  to  think  otherwise,  one 
would  naturally  attribute  to  contact  infection  the  chief  role 
in  the  extension  of  this  disease,  at  least  in  the  family.  The 
only  objection  is  offered  by  the  pathologists,  many  if  not 
most  of  whom  affirm  that  the  evidence  points  to  direct  infec- 
tion of  the  lungs  by  the  inspired  air.  There  are,  however, 
many  able  experimenters  who  think  otherwise,  and  who  main- 
tain that  tubercle  bacilli  may  enter  the  body  at  various  points 
and  reach  the  lungs  through  the  lymph  channels.  It  is  impos- 
sible for  the  writer  properly  to  weigh  pathological  evidence, 
but  that  the  question  is  still  sub  judice  must  be  admitted. 
Under  the  circumstances  it  seems  to  be  wise  to  assume 
as  a  working  hypothesis  that  contact  infection  is  a  factor  of 
great  importance  in  the  causation  of  human  tuberculosis.  It 
is  certainly  essential  to  guard  against  such  infection  in  every 
way,  and  from  a  person  who  does  thus  conduct  himself  in  a 
cleanly  manner  at  all  times,  diffusion  of  the  disease  through 
the  air  would  be  impossible.  Undue  emphasis  laid  upon  the 
invisible  and  therefore  terrifying  infection  in  the  air  has  done 
more  than  anything  else  to  develop  the  unfortunate  phthisi- 
phobia  which  so  often  renders  miserable  the  life  of  the  tuber- 
culous, and  seriously  interferes  with  rational  measures  for  the 
restriction  of  the  disease. 

1  Kavacs,  Zeiglers  Beitrage  zur.  Path.  Anat.,  1906,  XL. 

2  Preisich  and  Schiitz,  Berl.  klin.  Wschnschr.,  1902,  XXXIX,  466. 
'  Wassermann,  Berl.  klin.  Wchnschr.,  1908,  Nr.  48. 

*  Calmette  and  Landouzy,  Sixth  Internat.  Cong,  on  Tuberc,  Wash., 
1908,  I,  110. 


206         THE  SOURCES  AND  MODES  OF  INFECTION 

Importance  of  Contact  Infection.  —  I  have  sometimes  been 
told  that  I  lay  too  much  emphasis  on  contact  infection,  but 
if  it  is  the  principal  way  in  which  disease  spreads,  too  much 
emphasis  cannot  be  placed  upon  it,  and  it  seems  to  me  that 
the  evidence  is  that  it  is  the  chief  mode  of  infection.  Even 
if  it  is  not  so  important  as  is  here  alleged,  every  one  must 
admit  that  it  is  of  considerable  importance,  yet  until  recently 
very  little  attention  has  been  paid  to  it.  If  contact  infection 
is  the  chief  mode  of  extension  of  the  contagious  diseases,  then 
defense  against  them  becomes  more  largely  a  personal  affair 
than  we  have  been  taught.  We  do  not  have  to  rely  exclu- 
sively on  the  municipality  for  our  protection,  awaiting  forced 
isolation,  hospital  construction,  disinfection  and  the  like,  but 
can  largely  protect  ourselves  by  keeping  our  fingers  out  of 
our  mouths,  and  also  everything  else  except  what  belongs 
there.  It  may  not  be  possible  to  prevent  all  contagious  sick- 
ness in  this  way,  but  some  can  be  avoided,  and  perhaps  most 
of  it.  Contact  infection  is  avoided  by  personal  cleanliness, 
and  personal  cleanliness  is  demanded  by  decency,  good  man- 
ners and  refinement,  as  well  as  by  hygiene.  It  is  not  much 
trouble  to  be  decently  clean,  and  it  is  not  very  expensive. 
It  is  a  serious  mistake  to  build  an  expensive  isolation  hos- 
pital that  does  not  check  disease,  or  to  construct  a  filter  when 
it  is  not  needed ;  but  no  harm  would  be  done  if  the  views  here 
presented  should  be  found  to  be  erroneous  and  people  should 
learn  to  wash  their  hands  and  keep  their  fingers  out  of  their 
mouths  to  no  purpose  so  far  as  dis(^ase  prevention  is  concerned. 
It  seems  certain  that  much  can  be  done  to  prevent  the  spread 
of  disease  in  the  family  and  in  hospitals,  schools  and  institu- 
tions, if  only  personal  cleanliness  be  insisted  upon.  Yet  such 
cleanliness  or  medical  asepsis  is  sadly  neglected  by  physicians 
as  well  as  by  nurses.  Rather  strong  preaching  is  needed 
when,  as  was  referred  to  on  another  page,  a  typhoid  nurse  is 
detailed  for  the  double  duty  of  washing  bedpans  and  preparing 
food.  It  is  certainly  necessary  to  insist  somewhat  strenuously 
on  reform  when  such  occurrences  as  the  following  take  place. 


INFECTION  BY  CONTACT  207 

Disregard  of  Contact  Infection. —  Thus,  at  one  of  the  finest 
hospitals  in  this  country,  with  separate  wards  for  scarlet  fever 
and  diphtheria,  a  considerable  number  of  cases  have  arisen 
in  the  general  wards.  The  germs  were  supposed  to  be  air- 
borne, as  it  was  said  there  was  no  other  possible  avenue  of 
infection.  When  I  saw  the  head  nurse  lick  her  finger  to 
facilitate  turning  the  bedside  charts  of  diphtheria  patients,  I 
suspected  that  the  principles  of  medical  asepsis  had  not  been 
entirely  mastered.  Called  to  see  a  case  of  scarlet  fever  in  a 
well-to-do  family,  I  found  the  door  of  the  sick-room  carefully 
hung  with  a  sheet  to  keep  the  infection  from  the  other  chil- 
dren. After  examining  the  throat  with  a  spatula  I  handed 
the  latter  to  the  mother.  She  took  it  into  the  hall  and  put 
it  on  an  upholstered  sofa,  and  with  her  saliva-infected  hands 
opened  the  door  of  an  adjoining  room.  The  attending  physi- 
cian meanwhile  sat  on  the  bed  and  handled  the  patient,  an 
entirely  unnecessary  proceeding  at  that  time,  and  except  for 
the  example  set  him,  would  have  forgotten  to  wash  his  hands 
before  leaving.  A  certain  hospital  determined  to  copy  in  one 
of  its  wards  the  cubicle  system  of  the  French,  but  had  so 
missed  its  essential  features  that  I  found  doctors  and  nurses 
going  from  cubicle  to  cubicle  feeling  the  pulse,  smoothing  the 
bedclothes,  and  handling  dishes  without  even  stopping  to 
wash  their  hands.  Meanwhile  the  screen  was  supposed  to 
prevent  the  microbes  from  passing  from  bed  to  bed,  and  we 
all  carefully  wore  gowns  and  caps  so  that  the  wicked  little 
germ  might  not  jump  into  our  hair  and  then  jump  off  again 
onto  the  next  patient.  In  another  fine  hospital  for  conta- 
gious diseases,  where  great  stress  is  laid  upon  ample  space 
between  different  diseases  so  as  to  prevent  cross  infection, 
the  superintendent  was  observed  freely  to  touch  articles  about 
the  ward,  and  handle  the  patients,  and  then  go  to  the  public 
office  without  even  washing  his  hands.  Such  incidents  could 
be  multiplied  indefinitely.  The  superintendent  of  another  hos- 
pital invited  another  visitor  and  myself  to  eat  ice  cream  from 
the  same  spoon  as  himself,  which  spoon  was  then  replaced 


208        THE  SOURCES  AND  MODES  OF  INFECTION 

in  the  freezer  which  was  to  supply  the  wards.  I  was  most 
of  all  impressed  with  the  fact  that  at  the  International  Con- 
gress on  Tuberculosis  in  1908  a  large  number  of  the  readers 
of  papers  moistened  their  fingers  with  their  tongue  when  turn- 
ing the  pages,  and  in  each  of  the  sections  only  one  drinking 
glass  was  provided  for  all  the  speakers;  and  this  continued 
without  protest  for  a  day  or  two.  If  the  most  distinguished 
investigators  and  health  officials  of  the  world,  gathered  to 
study  the  most  important  contagious  disease,  show  no  appre- 
ciation whatever  of  the  importance  of  contact  infection,  it 
is  certainly  time  for  some  one  to  be  emphatic. 

Personal  Prophylaxis.  —  The  discovery  that  disease  germs 
are  rarely  able  to  maintain  themselves  outside  of  the  body 
clouded  the  hopes  of  those  who  expected  by  municipal  house 
cleaning  to  "  stamp  out  the  zymotic  diseases,"  and  the  later 
discovery  of  numerous  missed  cases  and  carriers  has  shown 
that  isolation  of  the  sick  controls  infection  far  less  than  was 
believed.  These  somewhat  discouraging  facts  are  to  a  large 
degree  offset  by  what  has  been  learned  of  the  modes  of 
infection.  Formerly  air  infection  was  chiefly  feared;  now  it 
appears  that  contact  infection  is  of  prime  importance.  For- 
merly dependence  was  placed  upon  the  state  to  isolate  and 
disinfect ;  now  it  appears  that  the  individual  can  protect  him- 
self, and  as  easily  protect  others  if  he  chance  to  be  infected. 
It  is  usually  comparatively  simple  so  to  live  as  not  to  allow 
the  secretions  of  others  to  come  in  contact  with  one's  own 
mucous  surfaces,  and  it  is  easy,  and  should  be  considered 
immoral,  to  allow  one's  own  secretions  to  be  so  placed  that 
they  may  infect  another.  Personal  cleanliness  is  less  expen- 
sive than  municipal  cleanliness,  and  is  within  the  reach  of  all. 

Need  of  Education.  —  When  one  notes  the  utter  disregard 
of  medical  as(!psis  shown  in  our  hospitals  and  medical  con- 
gresses, one  is  apt  to  feel  that  the  education  of  the  public  in 
habits  of  personal  cleanliness  will  take  a  very  long  time;  but 
some  encouragement  is  felt  when  it  is  remembered  that  it  is 
not  so  very  long  ago  that  excrement  was  commonly  thrown 


INFECTION  BY  CONTACT  209 

into  the  street  and  garbage  was  tossed  under  the  tables  of 
the  great.  It  is  only  a  few  years  since  our  sidewalks  were 
flecked  with  saliva,  but  now  nineteen  persons  out  of  twenty 
are  ashamed  to  be  caught  spitting  on  the  pavement.  Perhaps 
we  may  all  soon  learn  to  stop  distributing  our  secretions  so 
freely  among  our  friends. 

Education  in  School.  —  As  the  avoidance  of  contact  infec- 
tion is  chiefly  a  personal  matter,  the  present  need  is  for  educa- 
tion. First  of  all,  the  teachers  in  the  medical  schools  and  the 
staffs  of  hospitals  must  learn  to  appreciate  the  importance  of 
this  mode  of  infection.  It  is  not  unreasonable  to  hope  that 
in  a  few  years  the  schools  and  the  hospitals  will  place  as 
much  emphasis  on  medical  asepsis  as  they  now  do  on  surgical 
asepsis,  and  it  is  to  these  centers  that  we  must  look  for  the 
education  of  physicians,  health  officers  and  nurses.  To  edu- 
cate the  general  public  is  a  more  difficult  matter.  Some  years 
ago  Dr.  Theobald  Smith  called  my  attention  to  the  desirabil- 
ity of  teaching  school  children  something  about  the  require- 
ments of  personal  cleanliness,  and  since  then  I  have  each  year 
distributed  to  each  school  child  the  following  "  dont's  " 

REMEMBER    THESE    THINGS. 

Do  not  spit  if  you  can  help  it.  Never  spit  on  a  slate,  floor, 
or  sidewalk. 

Do  not  put  the  fingers  into  the  mouth. 

Do  not  pick  the  nose  or  wipe  the  nose  on  the  hand  or  sleeve. 

Do  not  wet  the  finger  in  the  mouth  when  turning  the  leaves 
of  books. 

Do  not  put  pencils  into  the  mouth  or  wet  them  with  the 
lips. 

Do  not  put  money  into  the  mouth. 

Do  not  put  pins  into  the  mouth. 

Do  not  put  anything  into  the  mouth  except  food  and  drink. 

Do  not  swap  apple  cores,  candy,  chewing  gum,  half-eaten 
food,  whistles  or  bean  blowers,  or  anything  that  is  put  into 
the  mouth. 


210       THE  SOURCES  AND  MODES  OF  INFECTION 

Never  cough  or  sneeze  in  a  person's  face.  Turn  your  face 
to  one  side. 

Keep  your  face  and  hands  clean;  wash  the  hands  with 
soap  and  water  before  each  meal. 

Providence,  May,  1901. 

An  explanatory  circular  is  sent  to  the  teachers,  and  of  late 
a  short  account  of  the  sanitary  reasons  for  personal  clean- 
liness has  been  distributed  to  children  above  the  primary 
grade.  Large  printed  copies  of  the  "  don'ts  "  have  been 
framed  and  hung  in  the  schoolhouses. 

Much  kindergarten  work  is  of  such  a  nature  as  to  inculcate 
rather  than  discourage  cleanly  habits.  Children  work  in 
common  in  moist  clay  and  sand,  use  the  same  "  gifts  "  and 
toys  and  are  brought  into  close  contact  in  the  games. 
Miss  Bessie  M.  Scholfield,  late  supervisor  of  these  schools 
in  Providence,  succeeded,  without  any  undue  expense  or 
violent  change  of  methods,  in  employing  kindergarten  work 
as  a  means  of  teaching  some  of  the  principles  of  personal 
hygiene. 

Municipality  should  encourage  Cleanliness.  —  Besides 
efforts  that  are  directly  educational  the  municipality  can  do 
much  indirectly  to  encourage  habits  of  personal  cleanliness 
and  to  prevent  the  distribution  of  the  secretions  and  excre- 
tions of  the  body.  The  common  drinking  cup  is  a  most 
efficient  means  of  such  distribution,  and  it  should  be  abol- 
ished in  all  schools  and  other  public  institutions.  This  has 
been  done  in  many  places,  and  individual  cups  or  specially 
designed  drinking  fountains  substituted.  The  example  is 
now  being  followed  ])y  some  railways,  factories  and  shops. 
The  states  of  Kansas,  Michigan  and  Mississippi  were  the 
first  to  forbid  the  use  of  a  common  drinking  glass  on  rail- 
ways, and  the  Lackawanna  and  some  other  roads,  and  the 
Pullman  Company  advertise  as  an  attraction  free  cups  of 
paraffin  paper  for  each  passenger.^     Since  the  above  was 

>  J.  of  Outdoor  Life,  1909,  VI,  371. 


INFECTION  BY  CONTACT      '  211 

written  a  dozen  other  states  have  forbidden  the  use  of  the 
common  glass.  Hundreds  of  churches  have  adopted  the 
individual  communion  cup.  In  the  first  edition,  I  said 
that  "  the  roller  towel  should  go  the  way  of  the  common 
drinking  cup."  Since  then  Massachusetts  and  Connecticut 
and  the  cities  of  New  York  and  Chicago  have  enacted 
statutes  or  adopted  rules  forbidding  the  use  of  a  common 
towel  in  public  places. 

People  are  more  likely  to  keep  clean  if  it  is  easy  to  do 
so.  Hence  the  establishment  of  public  baths  may  be  con- 
sidered a  real  sanitary  measure.  While  compulsion  can 
have  little  share  in  the  campaign  for  cleanliness,  certain 
prohibitions  are  entirely  reasonable  and  feasible.  Thus 
ordinances  against  spitting  on  the  sidewalks  and  the  floors 
of  public  places  have  done  much  to  teach  people  to  take 
proper  care  of  their  secretions.  Reference  has  already 
been  made  to  evidence  that  the  abolition  of  privy  vaults 
results  in  a  decrease  in  typhoid  fever.  Privy  vaults  cer- 
tainly encourage  the  improper  disposal  of  excreta  and 
general  uncleanly  habits.  A  good  sewage  system  and  the 
removal  of  vaults  and  cesspools  do  much  to  prevent  con- 
tact infection,  at  least  in  the  fecal-borne  diseases. 


CHAPTER  V. 

INFECTION    BY    FOMITES. 

Definition  of  Term.  —  As  was  shown  in  the  preceding 
chapter,  it  seems  very  probable  that  contagious  disease  may 
often  be  caused  by  the  quite  direct  transference  of  the  germs 
from  one  person  to  another  on  such  objects  as  cups,  pencils, 
pipes,  the  fingers,  etc.  This  mode  of  transference  should 
properly  be  considered  a  form  of  contact  infection.  The  term 
contact  infection,  as  commonly  used  at  the  present  time,  does 
not  necessarily  imply  the  immediate  touching  of  two  persons, 
but  it  does  imply  the  comparatively  direct  transference  of 
quite  fresh  material  from  one  to  another.  Although  almost 
any  object  may  in  this  manner  be  the  bearer  of  infection,  it 
would  not  ordinarily  be  considered  as  fomites.  By  fomites 
are  usually  meant  infected  obj'ects  which  retain  the  iiifection 
for  some  time.  A  toy  used  by  a  diphtheria  patient  and  sent 
to  a  distant  town  and  there  giving  rise  to  the  disease,  the 
dress  of  a  scarlet-fever  patient  put  away  for  weeks  or  months 
and  brought  out  only  to  cause  another  case,  a  library  book 
carrying  the  infection  of  smallpox  from  one  household  to 
another,  blankets  loaded  with  tyj)hoid  bacilli  in  South  Africa 
transferring  infection  to  England,  infected  hides  from  Asia 
causing  anthrax  in  Philadelphia,  blank  cartridges  as  the  bear- 
ers of  tetanus  germs,  and  the  various  objects  in  a  room  lately 
occupied  by  a  case  of  any  contagious  disease  giving  rise  to 
the  same  affection  in  newcomers,  would  all  be  recognized  as 
fomites.  The  cup  which  carries  the  moist  saliva  from  one 
school  child  to  another,  the  borrowed  pencil  which  transfers  the 
fresh  syphilitic  virus  from  lip  to  lip,  and  the  urine-moistened 
closet  seat  which  infects  the  fingers  and  then  the  mouth  of 
the  next  user,  arc  not  thought  of  as  fomites  but  as  the  neces- 

212 


INFECTION  BY  FOMITES  213 

sary  media  for  that  intimate  mode  of  disease  transference 
which  is  coming  to  be  called  contact  infection.  This  dis- 
tinction between  the  two  classes  of  bearers  of  infection  is 
somewhat  arbitrary,  and  not  very  definite,  but  is  eminently 
practical.  In  this  book,  by  infection  by  fomites  is  meant  a 
transference  of  infecting  material  on  objects  under  such  con- 
ditions that  considerable  time  elapses,  days  at  least,  usually 
weeks,  sometimes  months. 

Yellow  Fever  and  Fomites.  —  If  one  takes  up  the  older 
text-books  on  yellow  fever  it  will  be  found  that  fomites  were 
considered  the  most  important  means  in  the  extension  of  this 
disease.  The  invasion  of  cities  and  countries  was  usually 
attributed  to  this  mode  of  carriage.  This  was  the  general 
view  up  to,  and  indeed  after,  the  discovery  of  the  role  played 
by  the  mosquito,  and  numerous  instances  of  such  transference 
are  given.  Thus  the  federal  inspectors^  attributed  the  out- 
break at  Brunswick,  Ga.,  to  ballast  brought  from  Cuba.  The 
disease  was  supposed  to  have  been  carried  from  New  Orleans 
to  Havana  by  means  of  second-hand  oyster  buckets."  Lice- 
aga^  gives  instances  of  the  transmission  of  yellow  fever  by 
a  shipload  of  grain  from  New  Orleans,  by  cloth  spread  out 
on  the  grass  to  dry,  by  general  merchandise,  by  bagging,  by 
clothing,  and  by  ballast.  Horlbeck*  says  that  two  persons 
at  Key  West  contracted  yellow  fever  from  sleeping  on  a  mat- 
tress that  was  brought  from  Cuba. 

Never  so  Transmitted.  —  In  all  these  instances  the  evi- 
dence is  the  same :  a  locality  has  long  been  free  from  yellow 
fever,  something  is  imported  from  an  infected  place  and  the 
disease  develops.  What  could  be  clearer?  The  proofs  that 
it  is  a  fomites-borne  disease  were  far  more  numerous  and 
stronger  for  yellow  fever  than  for  almost  any  other  disease. 

1  Rep.  Surg.  Gen.  U.  S.  Mar.  Hosp.  Serv.,  1893,  II,  33. 
^  Report  on  Shipment  of   Merchandise,    U.  S.   Mar.   Hosp.  Serv., 
Special  Report,  1899,  9. 

'  Liceaga,  Am.  Pub.  Health  Ass.  Rep.,- 1898,  XXIV,  122. 
*  Horlbeck,  Am.  Pub.  Health  Ass.  Rep.,  1897,  XXIII,  436. 


214         THE  SOURCES  AND  MODES  OF  INFECTION 

Yet  we  now  know  that  yellow  fever  never  was,  nor  could  be, 
transmitted  in  any  such  way.  Such  a  mistake,  a  mistake  which 
cost  millions  upon  millions  because  of  the  needless  interrup- 
tion of  commerce,  and  disinfection,  should  make  us  careful 
how  on  similar,  but  weaker,  evidence  we  attribute  importance 
to  fomites  as  a  means  of  infection  in  other  diseases,  and  should 
lead  us  to  inquire  what  proof  there  is  that  the  long  persist- 
ence of  infection  on  things  is  a  weighty  factor  in  the  trans- 
mission of  disease. 

Smallpox.  —  It  does  not  require  much  search  in  medical 
literature  to  find  numerous  instances  of  the  alleged  trans- 
mission of  disease  by  fomites.  Recent  text-books  and  jour- 
nals are  full  of  them.  Welch  and  Schamberg^  state  that 
smallpox  was  brought  to  Philadelphia  on  cotton  from  the 
South,  but  the  only  reasons  for  thinking  so  were  that  there 
was  much  smallpox  in  the  cotton  region  and  none  in  Phila- 
delphia, and  that  the  patient  handled  cotton.  Not  long  since 
the  health  officer  of  a  western  city  reported  that  the  principal 
source  of  smallpox  in  that  city  was  lumber,  his  assumption 
being  based  on  the  facts  that  there  was  much  of  the  disease 
in  the  lumber  camps,  that  the  rough  lumber  was  well  fitted 
to  carry  contagion,  and  that  in  most  families  the  first  person 
attacked  was  engaged  in  some  sort  of  woodworking.  The 
above  are  fair  samples  of  the  kind  of  evidence  on  which  the 
theory  of  fomites  infection  rests.  Smith "  reports  that  a  man 
from  Paris  died  in  London  of  what  was  probably  malignant 
smallpox.  Two  people  who  afterwards  slept  in  the  same  bed, 
on  different  days,  developed  the  disease,  as  did  the  girl  who 
sorted  at  the  laundry  the  soiled  linen  from  this  hotel. 

Scarlet  Fever.  —  A  recent  writer  in  Public  Health^  reports 
six  instances  of  house  infection  giving  rise  to  scarlet  fever, 
in  one  case  nine  months  after  the  first  patient  was  sick.    The 

1  Welch  and  Schamberg,  The  Acute  Infectious  Diseases,  Phila.,  1905, 
160. 

'  Smith,  Pul).  Iloalth,  Lond.,  1001-02,  XIV,  211. 
»  Trotter,  Pub.  Health,  Lond.,  1906-07,  XIX,  745. 


INFECTION  BY  FOMITES  215 

only  evidence  was  the  recurrence  of  the  disease  in  the  house. 
Welch  and  Schamberg^  quote  from  others  reports  of  fomites 
infection  in  this  disease.  Boeck  states  that  the  hair  of  a 
scarlet-fever  patient  caused  the  disease  twenty  years  after. 
Another  physician  caught  the  disease  from  a  coat  which  he 
wore  while  attending  a  case  a  year  and  a  half  before.  The 
health  officer  of  Detroit^  reports  two  cases  due  to  infection 
from  books  which  had  been  used  by  a  patient  some  months 
before.  Wende^  states  that  quilts  used  by  scarlet-fever 
patients  in  August,  and  put  away  without  disinfection, 
caused  the  disease  in  November.  The  reports  of  the  state 
board  of  health  of  Michigan*  give  instances  of  the  per- 
sistence of  the  scarlet-fever  virus  for  years  in  houses,  letters, 
books,  etc. 

Diphtheria.  —  Buckley^  quoted  from  the  Newton,  Vic- 
toria, Health  Report  an  instance  where  a  cornet  used  by  a 
diphtheria  patient  was  put  away  for  four  years,  and  was  then 
found  by  some  children,  who  contracted  the  disease  from  it. 
He  gives  another  instance  where  the  disease  recurred  in  the 
house  after  a  period  of  two  years.  At  a  time  when  Manila 
was  absolutely  free  from  diphtheria,  an  American  child  who 
had  been  there  over  a  year  received  some  Christmas  presents 
from  St.  Louis,  and  was  taken  sick  a  few  days  later.  Chris- 
tian*' writes  of  the  transmission  of  diphtheria  on  carpenters' 
tools  which  were  sent  from  one  shop  to  another. 

Cholera.  —  A  number  of  instances  of  the  transmission  of 
cholera  by  soiled  clothing  are  given  in  the  Report  of  the 
Marine  Hospital  Service  for  1893.^  In  nearly  every  instance 
the  clothing  was  brought  from  foreign  countries.     Because 

*  Welch  and  Schamberg,  The  Acute  Infectious  Diseases,  Phila.,  1905, 
344. 

»  Rep.  Bd.  of  Health,  Detroit,  for  year  ending  June  30,  1903,  11. 
«  Buflfalo  San.  Bull.,  Nov  30,  1908. 

*  Rep.  St.  Bd.  Health,  Mich.,  1906,  134;  1907,  133. 
»  Pub.  Health,  Lond.,  1906-07,  XIX,  296. 

*  Bull.  N.  Y.  St.  Board  of  Health,  June,  1907,  5. 

'  Rep.  Surg.  Gen.  U.  S.  Mar.  Hosp.  Serv.,  1893,  Vol.  II,  353. 


216         THE  SOURCES  AND  MODES  OF  INFECTION 

a  company  of  soldiers  had  suffered  from  tj^phoid  fever  for 
two  years,  and  the  disease  ceased  on  disinfecting  the  bar- 
racks, the  outbreak  was  beheved  to  have  been  due  to  room 
infection.^ 

Before  weighing  the  value  of  this  evidence  it  is  perhaps 
worth  while  to  consider  some  of  the  things  which  are  most 
often  alleged  to  serve  as  fomites. 

Infected  Clothing.  —  From  the  time  when  the  priest  was 
directed  how  to  detect  leprosy  in  woolen  and  linen^  to  the 
present,  clothing  has  been  considered  an  important  vehicle 
of  infection.  It  is  not  to  be  doubted  that  disease  germs  may 
be  carried  on  clothing.  If  clothing  is  soiled  with  a  consider- 
able quantity  of  infected  saliva,  feces,  urine  or  pus,  and  if 
while  fresh,  say  within  a  few  hours  or  days,  it  is  brought  in 
contact  with  susceptible  persons,  disease  may  result.  If  it  is 
folded  and  put  away  in  the  dark,  especially  if  it  be  in  a  damp 
place,  it  may  remain  infectious  perhaps  for  months.  But  as 
bacteria  as  a  rule  die  rapidly,  and  as  there  must  be  a  sequence 
of  gross  infection,  favorable  conditions  for  survival,  and  con- 
tact with  susceptible  persons,  it  does  not  seem  likely  that 
disease  is  often  caused  in  this  way. 

Many  instances  are  recorded,  usually  only  of  possible,  rarely 
of  probable,  transference  of  disease  by  clothing.  Of  yellow 
fever  more  than  of  anj^  other  disease  has  this  been  alleged,  yet 
we  now  know  that  such  transmission  of  this  disease  is  impos- 
sible. Many  writers  also  report  the  spread  of  bubonic  plague 
by  means  of  clothing,  but,  as  will  be  seen,  the  evidence  is  that 
plague  is  only  under  very  exceptional  circumstances  carried 
by  fomites. 

Typhus  not  carried  in  Clothing.  —  When  typhus  fever 
appeared  in  New  York  in  1S92,  from  sixty  to  seventy-five 
officers  of  the  health  department  were,  according  to  Doty,^ 

'  Cited  by  Germano,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz., 
1897,  XXIV,  404. 

2  Leviticus,  Chapter  xiii,  verses  47-.')n. 

>  Doty,  Med.  News,  N.  Y.,  1905,  LXXXVI,  730. 


INFECTION  BY  FOMITES  217 

more  or  less  in  contact  with  tiie  cases,  often  in  intimate 
contact;  gowns  were  not  used,  and  the  officials  went  freely 
between  the  patients  and  their  own  homes,  and  about  their 
other  business,  yet  no  case  of  this  disease  could  be  traced  to 
fomites  infection. 

Butler  ^  speaks  of  a  parlor  maid  in  a  contagious-disease 
hospital  who  for  six  months  had  been  in  daily  contact  with 
nurses  coming  directly  from  scarlet-fever  cases  without 
change  of  clothes,  but  she  did  not  contract  the  disease  until 
exposed  to  an  incipient  case  in  the  person  of  a  nurse,  when 
she  promptly  developed  scarlet  fever.  This  is  only  one 
illustration  of  many  of  the  failure  of  supposedly  infected 
clothing  to  infect. 

Physicians  rarely  carry  Disease.  —  In  scarlet  fever  and 
diphtheria  physicians  are  constantly  passing  from  the  sick 
to  the  well.  Some  of  them  take  great  precautions  to  avoid 
carrying  the  disease  in  their  clothes,  but  the  majority  take 
few  or  none,  —  or  at  least  did  not  until  very  recently. 
Yet  records  of  their  transmitting  disease  are  extremely 
rare.  For  many  years  I  was  on  the  lookout  for  this  mode 
of  transference,  and  only  once  or  twice  found  any  evidence 
that  the  physician  was  at  fault.  In  such  cases  how  much 
greater  is  the  chance  that  the  physician  carries  infection  on 
his  hands  than  in  his  clothes.  Barlow  ^  found  that  of  500 
cases  of  scarlet  fever  in  only  4  had  the  physician  previously 
been  treating  the  disease  and  these  4  cases  were  apparently 
traced  to  other  sources. 

Infection  by  Clothing  is  Rare.  —  If  the  gross  infection  of 
clothing  is  only  in  rare  instances  the  cause  of  disease,  how 
little  must  be  attributed  to  slight  infection !  A  few  droplets 
of  tuberculous  saliva,  a  slight  smear  of  moisture  from  the 
lips  of  a  diphtheria  patient,  will  soon  lose  their  virulence  after 
exposure  to  light  and  air.  But  usually  the  visitor  in  a  sick- 
room will  escape  all  infection  except  the  hypothetical  floating 

1  Butler,  Proc.  Roy.  Soc.  Med.,  Lond.,  1908,  I,  Epidemiol.  Sect.,  225. 

2  Barlow,  Med.  Officer,  1910,  III,  319. 


218  THE  SOURCES  AND  MODES  OF  INFECTION 

particles.  The  danger  from  this  floating  matter  will  be  shown 
in  another  chapter  to  be  a  negligible  quantity.  It  is  the  com- 
mon practice  for  physicians,  nurses  and  visitors  in  a  room 
occupied  by  a  contagious  case  to  wear  a  gown  and  cap.  For 
physicians  and  nurses  who  are  to  move  or  lift  the  patient,  or 
otherwise  come  into  intimate  contact  with  him,  the  gown  is 
a  reasonable  protection  against  possible  gross  contamination. 
For  the  careless  visitor  too  it  may  be  useful.  The  cap  is  a 
useless  frivolity.  It  is  amusing  to  see  how  religiously  it  is 
worn,  while  no  protection  is  given  the  feet,  though  Denny 
and  Nyhen  ^  have  shown  that  infection  by  means  of  the  shoes 
is  bacteriologically  possible,  while  the  aerial  infection  of  the 
hair  has  never  been  demonstrated  and  is  highly  improbable. 
More  than  once  have  I  seen  a  physician  don  his  cap  to  keep 
the  germs  from  flying  into  his  hair,  and  pass  freely  from  one 
diphtheria  patient  to  another,  inspecting  the  throat,  feeling 
the  pulse  or  smoothing  the  bedclothes,  and  occasionally 
stroking  his  own  chin  or  scratching  his  head,  all  without 
washing  his  hands.  And  physicians  and  nurses  will  continue 
to  do  such  things  as  long  as  they  fancy  that  air  infection  is 
all  they  have  to  fear,  and  forget  that  there  is  such  a  thing  as 
contact  infection.  It  has  for  some  years  been  my  custom 
not  to  wear  a  gown  when  called  in  consultation  to  cases  of 
contagious  disease,  or  when  visiting  hospital  wards,  unless  I 
am  to  do  much  work  about  the  patient.  Under  the  condi- 
tions of  a  casual  visit,  qven  in  smallpox,  I  do  not  wear  a 
gown.  It  is  not  necessary  to  touch  anything  except  with  the 
hands,  and  these  should  be  carefully  washed  before  leaving. 
I  have  never  carried  infection  to  my  home,  or  elsewhere  so 
far  as  known,  and  I  believe  that  there  is  no  chance  of  my 
doing  so. 

Laundries  and  Disease.  —  If  clothing  can  carry  infection, 

sickness  ought  to  make  its  appearance  in  laundries,  to  which 

enormous  quantities  of  clothing  go  even  while  the  infecting 

material  is  still  fresh.     Attempts  have  been  made  to  show 

'  J.  Mass.  Ass.  Bds.  of  Health,  Bost.,  1904,  XIV,  109. 


INFECTION  BY  FOMITES  219 

that  disease  is  carried  to  laundry  workers  in  this  way,  and 
it  is  probable  that  some  of  the  alleged  instances  are  true. 
Thus  Sedgwick,  and  also  Walcott,^  report  cases  of  typhoid 
fever  where  the  evidence  was  very  strong  that  the  disease 
was  contracted  by  handling  soiled  linen.  Thorne-Thorne  ^ 
also  reports  an  interesting  case  of  probable  transmission  of 
typhoid  fever  by  clothing.  That  such  accidents  are  common 
has  never  been  shown.  Certainly  in  Providence  there  is  no 
excess  of  scarlet  fever,  diphtheria  or  typhoid  fever  among 
laundry  workers.  This  cannot  be  due  to  the  disinfection  of 
the  clothing,  for  much  disinfection  is  not  effective,  and  for 
six  years  there  has  been  no  disinfection  after  diphtheria, 
and  moreover  the  linen  from  carriers  and  missed  cases  is 
nowhere  subjected  to  disinfection. 

It  is  true  that  Landouzy,^  after  examining  1590  laundry 
workers  in  Paris,  states  that  tuberculosis  is  twice  as  prevalent 
among  them  as  among  other  workers,  and  he  attributes  it  to 
infection  from  soiled  clothing.  But  certainly  other  occu- 
pations show  an  even  greater  excess  of  this  disease,  an-d 
there  is  no  suggestion  that  it  is  due  to  infection  from  the 
materials  handled.  There  may  be  many  other  reasons  why 
laundry  workers  should  show  an  excess  of  tuberculosis,  such 
as  age  distribution,  poverty  and  overwork. 

Infection  of  Rooms.  —  It  is  generally  believed  that  the 
room,  or  rooms,  which  have  been  occupied  by  a  case  of  con- 
tagious disease  are  a  fertile  source  of  danger  to  others.  The 
germs  of  diphtheria,  scarlet  fever  and  smallpox  are  sup- 
posed to  become  attached,  not  only  to  books,  playthings, 
bedding  and  furniture,  but  also  to  the  walls  and  ceilings.  It 
is  true  that  anything  which  can  be  reached  by  the  patient 
or  attendant  may  possibly  receive  infection,  the  chance  in- 
creasing according  to  the  frequency  with  which  the  thing  is 

*  Sedgwick  and  Walcott,  J.  Mass.  Ass.  Bds.  Health,  Boston,  1900, 
IX,  145. 

2  Thorne-Thorne,  Clin.  Soc.  Trans.,  Lond.,  1892,  XXV,  SuppL,  67. 
'  Landouzy,  Presse  med..  Par.,  1905,  XIII,  633. 


220         THE  SOURCES  AND  MODES  OF  INFECTION 

handled.  That  parts  of  the  room  or  its  contents  not  touched 
should  be  infected  by  floating  particles,  is  highly  improbable. 
The  secretions  and  excretions  which  in  various  ways  become 
attached  to  the  contents  of  the  room  are  usually  small  in 
amount  and  thinly  smeared  on  the  surface.  Such  material 
usually  rapidly  loses  its  virulence  by  drying,  so  that,  as  is 
shown  in  these  pages,  virulent  germs  are  recovered  from  the 
sick-room  in  only  a  small  proportion  of  tests.  Nevertheless 
if  people  should,  after  the  termination  of  the  sickness,  crowd 
into  the  room,  rub  their  moistened  fingers  over  the  various 
objects  and  put  the  fingers  in  the  mouth,  infection  might 
sometimes  result.  But  as  the  germs  die  rapidly,  as  probably 
not  many  persons  enter  the  room,  as  even  visitors  would 
usually  run  little  chance  of  taking  up  whatever  pathogenic 
organisms  might  be  there,  we  are,  I  think,  justified  in  assum- 
ing that  infection  from  the  room  or  its  contents  is  not  very 
likely  to  take  place. 

"  Lung  Blocks."  —  The  celebrated  "  lung  block  "  in  New 
York,  bounded  by  Cherry,  Catherine,  Market  and  Hamilton 
streets,  has  had  enormous  influence  on  modern  views  con- 
cerning the  transmission  of  tuberculosis.  The  great  excess 
of  tuberculosis  in  certain  tenement  houses  has  given  rise  to 
a  strong  belief  in  its  causation  by  infection  which  remains 
attached  to  the  interior  of  the  dwelling.  We  even  hear  much 
loose  talk  about  the  germs  of  the  disease  developing  in  the 
filth  and  dampness  of  these  dark  houses.  What  an  important 
factor  house  infection  is  believed  to  be  in  the  causation  of 
this  disease  is  well  illustrated  by  the  exceedingly  prominent 
place  which  is  given  to  room  disinfection.  To  judge  from  the 
attention,  time  and  money  bestowed  on  room  disinfection 
after  the  removal  or  death  of  a  consumptive,  this  practice 
is  considered  of  equal  importance  with  hospitals,  sanatoriums, 
dispensaries  or  district  nursing  as  a  preventive  measure.  Let 
us  see  what  is  the  evidence  on  which  house  infection  is  sup- 
posed to  rest.  It  is  apparently  that  cases  continue  to  occur 
in  the  same  house  during  successive  years.    This  judgment 


INFECTION  BY  FOMITES  221 

is  based  on  the  spot  map.  Thus  in  New  York^  during  five 
years,  42  per  cent  of  the  deaths  from  tuberculosis  occurred  in 
23  of  the  total  houses  infected,  or  in  5.25  per  cent  of  all  the 
houses  in  the  city.  In  Ward  IV,  55.8  per  cent  of  the  cases 
occurred  in  10.5  per  cent  of  the  houses  in  the  ward  and  in  28 
per  cent  of  the  infected  houses.  In  Ward  VI,  44.7  per  cent  of 
the  cases  were  in  7  per  cent  of  the  total  houses  and  in  19 
per  cent  of  the  infected  houses.  Many  in  other  cities  have 
noted  the  same  phenomenon,  but  it  has  been  especially  well 
recorded  by  the  New  York  Department  of  Health.  But  to 
say  that  these  facts  are  to  be  largely  explained  by  the  per- 
sistence of  the  tubercle  bacilli  in  the  houses  is  no  more  rea- 
sonable than  it  would  be  to  explain  the  recurrence  of  an  excess 
of  murders  in  certain  areas  to  the  persistence  of  a  hypothet- 
ical microbe  of  homicide.  It  is  true  that  the  advocates  of 
the  importance  of  house  infection  point  to  numerous  in- 
stances in  which  an  apparently  healthy  family  moving  into 
a  house  recently  occupied  by  a  consumptive  later  develop 
the  disease.  That  such  should  quite  often  happen  merely  as 
a  coincidence  is  necessitated  by  the  great  prevalence  of  the 
disease.  That  in  "  lung  blocks  "  exposure  to  living  cases  in 
the  other  tenements  is  a  much  more  likelj^  source  of  the 
disease  than  exposure  to  bacilli  on  the  walls,  is  probable.  To 
demonstrate  the  relation  of  the  disease  to  house  infection  it 
would  be  necessary  to  go  fully  into  the  history  of  at  least  a 
large  proportion  of  the  cases,  and  that,  particularly  as  we 
really  know  nothing  about  the  latent  period  of  the  disease, 
is  at  present  impossible.  The  excessive  incidence  of  tubercu- 
losis on  certain  houses  is  no  proof  of  house  infection,  and  we 
are  obliged  to  appeal  to  the  facts  of  bacteriology  and  the 
general  principles  of  infection  to  estimate  the  probable  dan- 
ger from  this  source.  When  we  consider  the  number  of  per- 
sons who  are  continually  throwing  off  great  numbers  of 
tubercle  bacilli,  and  the  numberless  chances  there  are,  particu- 
larly in  the  crowded  tenement  districts,  of  coming  in  contact 
'  Rep.  Dept.  Health,  City  of  New  York,  1896,  244. 


222        THE  SOURCES  AND  MODES  OF  INFECTION 

with  fresh  infective  material,  there  seems  to  be  no  necessity 
of  assuming  that  infection  must  be  traced  to  the  more  or  less 
feeble  and  scattered  germs  that  may  be  clinging  to  the  walls 
of  a  vacated  apartment.  What  necessity  or  excuse  is  there 
for  assuming  that  such  infection  plays  more  than  an  inap- 
preciably minute  part  in  the  causation  of  this  disease  ? 

Rags  and  Disease.  —  Rags  have  often  been  considered  an 
important  vehicle  of  disease.  At  one  time  much  attention 
was  given  to  this  subject  in  the  United  States,  and  great 
danger  was  apprehended  from  the  importation  of  foreign  rags, 
and  stringent  measures  were  taken  to  secure  their  disinfec- 
tion. Lengthy  discussions  of  the  matter,  and  references  to  a 
great  volume  of  literature,  may  be  found  in  a  report  for  the 
New  York  City  Board  of  Health  by  Smith  in  1886,  and  in  the 
Marine  Hospital  Report  for  1893.^  Numerous  references 
are  given  of  the  alleged  transmission  of  various  diseases  by 
means  of  rags.  Among  the  diseases  mentioned  are  smallpox 
(126  outbreaks),  influenza,  scarlet  fever,  erysipelas,  typhoid 
fever,  septicemia,  cholera,  and  a  disease  peculiar  to  rag  dust, 
called  "  flock  cough." 

Rags  and  Smallpox.  —  It  has  been  believed  that  small- 
pox is  frequently  introduced  among  the  workers  in  paper 
mills  by  the  rags  which  they  handle.  Numerous  instances 
have  been  reported  from  Maine,  Massachusetts  and  Wiscon- 
sin, as  well  as  from  foreign  countries.  Most  of  the  evidence 
is  very  inconclusive,  as  no  effort  is  made  to  exclude  other 
sources  of  infection,  and  the  disease  is  usually  prevailing 
generally  at  the  time.  The  most  suggestive  outbreaks  are  a 
series  reported  by  the  Massachusetts  State  Board  of  Health.^ 
Here  from  one  to  three  cases  occurred  in  six  mills  in  different 
localities  at  a  time  when  there  was  no  smallpox  in  the  town. 
Dr.  Abbott,  who  personally  studied  these  outbreaks,  was  con- 
vinced that  they  were  due  to  handling  rags.  Yet  it  is  curious 
that  almost  nothing  has  been  heard  of  this  sort  of  infection 

'   Rep.  Surg.  Gen.  U.  S.  Mar.  Hosp.  Serv.,  1893,  II,  330. 
«  Rep.  SI.  Hd.  Mass.,  1888,  xvi. 


INFECTION  BY  FOMITES  223 

during  the  last  twenty  years,  and  this  at  a  time  when  small- 
pox was  of  a  remarkably  mild  type  and  great  quantities  of 
clothing  worn  by  patients  must  have  escaped  disinfection. 
Abbott  was  also  convinced  that,  owing  to  the  length  of  time 
between  the  collection  of  the  rags  and  the  opening  of  the 
bales,  no  danger  was  to  be  apprehended  from  foreign  rags. 
Doty^  says  "  that  the  most  careful  investigation  has  failed 
to  present  satisfactory  evidence  that  either  foreign  or  domes- 
tic rags  act  as  a  medium  of  infection."  He  has  personally 
carefully  studied  the  question  in  Egypt,  where  many  rags  are 
collected  for  the  American  market,  and  he  says  that  there  is 
no  evidence  of  the  infection  of  the  handlers  of  even  the  fresh 
rags. 

Rugs  and  Plague.  —  Remlinger'  has  recently  called  atten- 
tion to  the  supposed  danger  to  be  apprehended  from  draper- 
ies, and  particularly  also  rugs,  from  the  Orient.  He  rightly 
says  that  many  of  the  rugs  are  very  filthy,  and  must  have 
been  infected  during  their  use  or  manufacture.  Yet  during 
all  the  prevalence  of  cholera  and  bubonic  plague  in  Asia  dur- 
ing recent  years  not  a  single  case  of  these  diseases  has  been 
brought  into  Europe  or  America  in  this  way,  though  great 
quantities  of  rugs,  draperies  and  rags  have  been  imported 
without  disinfection  or  with  very  imperfect  disinfection. 

Money  and  Disease.  —  Money  is  popularly  believed  to  be 
a  common  means  of  spreading  disease.  Indeed  there  are  few 
things  which  at  first  sight  seem  more  likely  to  do  so  than  paper 
money.  Germs  readily  become  attached  to  its  surface,  it 
passes  rapidly  from  one  person  to  another,  it  is  kept  in  inti- 
mate contact  with  the  person,  held  closely  in  the  hand  and 
often  put  to  the  lips.  Nevertheless  there  is  no  good  evidence 
that  money  has  ever  actually  been  the  means  of  spreading 
contagious  disease.  If  money  is  frequently  a  carrier  of  infec- 
tion, persons  who  handle  a  great  deal  of  money  ought  to  be 
particularly  subject  to  infectious  disease.    This  does  not  seem 

1  Doty,  Med.  Rec,  N.  Y.,  1900,  LVIII,  681. 

*  Remlinger,  Hyg.  gen.  et  appliq.,  Par.,  1907,  II,  257. 


224        THE  SOURCES  AND  MODES  OF  INFECTION 

to  be  the  case,  though  there  are  unfortunately  no  good  pub- 
hshed  statistics  bearing  on  the  subject.  However,  it  is  the 
business  of  the  supporters  rather  than  the  opponents  of  the 
theory  to  produce  the  figures.  I  have  been  on  the  lookout 
for  contagious  disease  among  bank  clerks,  but  the  very  few 
cases  that  have  come  to  my  knowledge  during  the  past 
twenty-five  years  have  evidently  been  contracted  in  other 
ways.  According  to  Hilditch,^  the  "United  States  treasurer, 
who  has  given  the  subject  long  and  careful  consideration,  is 
emphatic  in  his  statement  that  '  there  is  not  the  slightest  evi- 
dence to  show  that  the  employees  in  his  department  contract 
infectious  diseases  any  oftener  than  others  who  are  not  in 
this  line  of  work.'  "  It  may  be  argued,  and  there  is  some 
truth  in  this,  that  tellers  are  accustomed  to  take  considerable 
precaution,  such  as  keeping  the  fingers  away  from  the  lips 
and  washing  the  hands  before  eating.  Tram-car  conductors 
are,  however,  I  know  from  observation,  particularly  prone  to 
hold  bills  and  coins  between  the  lips,  and  are  in  other  ways 
extremely  careless,  yet  they  certainly  show  no  excess  of  scarlet 
fever,  diphtheria  or  smallpox.  A  bacteriological  study  of 
paper  money  has  been  made  by  Hilditch  above  referred  to. 
He  examined  twenty-four  bills  and  found  the  number  of  bac- 
teria varied  from  14,000  to  586,000  per  bill.  Pus  bacteria 
wore  found,  as  was  to  have  been  expected,  but  no  other  patho- 
genic forms.  Hilditch  could  find  accounts  of  only  four  other 
similar  investigations,  none  of  which,  however,  were  as 
thorough  as  his.  Bacteria  are  not  found  in  any  large  num- 
bers on  coins,  chiefly  because  of  the  germicidal  action  of  the 
metal,  as  shown  by  the  researches  of  Park,^  Vincent '  and 
Bolton. 

Much  Evidence  Unsatisfactory.  —  It  would  be  easy  to  find 
hundreds  of  aiiegcMl  instances  of  fomites  infection,  in  some 
of  which  tlio  infection  was  supposed  to  have  persisted  for 

1  Hilditch,  Pop.  Sc.  Month,  N.  Y.,  1908,  LXXIII,  1.57. 

2  edited  by  Hilditch. 

^  Vincent,  Abst.  Med.  News,  N.  Y.,  1892,  LXXX,  275 


INFECTIOX  BY  FOMITES  225 

years.  Those  mentioned  in  the  preceding  pages  are  only  a 
few  which  I  happened  to  have  at  hand.  In  most  of  them 
there  is  no  real  evidence  that  the  disease  was  produced  in  the 
manner  claimed.  The  error  made  in  claiming  so  much  for 
fomites  infection  in  yellow  fever  shows  how  great  is  the  lia- 
bility of  error  for  other  diseases. 

Persons,  not  Things,  are  Dangerous.  —  It  must  also  be 
borne  in  mind  that  in  very  many  of  the  reported  cases  the 
supposed  infected  articles  were  carried  by  some  person.  That 
the  person  may  be  the  "carrier"  of  living  germs  on  his  own 
mucous  surfaces,  though  showing  no  symptoms,  we  now  know 
full  well.  Until  recently  this  was  not  known,  hence  it  was 
universal  to  consider  things,  not  persons,  as  the  bearers  of 
infection.  We  can  now  see  that  persons  in  whom  the  germs 
are  growing  are  much  more  likely  to  be  the  agents  of  infec- 
tion than  are  things  on  which  the  germs  are  dying.  Some  of 
the  instances  of  alleged  fomites  infection,  such  as  the  room 
infection  in  scarlet  fever  referred  to,  are  doubtless  really 
instances  of  carrier  infection. 

Fomites  and  Tetanus.  —  It  is  not  for  a  moment  to  be 
assumed  that  there  are  no  instances  of  fomites  infection.  It 
is  not  impossible,  or  at  all  improbable,  that  occasionally 
typhoid  fever,  smallpox,  diphtheria  and  other  diseases  are 
caused  by  material  things  holding  the  living  bacteria  for  some 
weeks  or  even  for  months.  In  some  instances  the  clinical 
evidence  of  fomites  infection  is  very  strong,  though  perhaps 
it  can  rarely  if  ever  be  in  any  individual  instance  entirely 
conclusive.  If  it  can  be  substantiated  by  bacteriological  evi- 
dence, it  becomes  so  much  the  stronger.  The  strongest  evi- 
dence we  have  of  fomites  infection  is  concerning  anthrax  and 
tetanus.  This  is  not  surprising  when  it  is  recalled  that  the 
bacilli  of  both  of  these  diseases  are  spore-forming  and  capable 
in  that  state  of  resisting  unfavorable  conditions  of  life  for 
years.  Thus  Smith  ^  finds  that  tetanus  bacilli  will  survive 
boiling  for  sixty  minutes  at  a  time,  or  twenty  minutes  on 
1  Smith,  Theobold,  J.  Am.  M.  Ass.,  Chicago,  1908,  L,  929, 


226        THE  SOURCES  AND  MODES  OF  INFECTION 

each  of  three  successive  days.  This  explains  why  they  have 
been  found  ahve  and  virulent  in  commercial  gelatine  and  in 
that  situation  have  been  known  to  give  rise  to  the  disease  in 
human  beings.^  Of  six  samples  of  cotton  lamp  wick  pur- 
chased in  various  shops  in  Havana,  five  were  shown  by  the 
inoculation  of  white  mice  to  be  infected  with  tetanus.  This 
material  was  used  by  midwives  for  tying  the  umbilical  cord, 
and  after  sterile  material  was  furnished  them  by  the  depart- 
ment of  health  it  is  said  that  almost  no  deaths  from  infantile 
tetanus  occurred  in  Havana.^  The  number  of  deaths  from 
tetanus  in  children  under  one  year  of  age  in  Havana  decreased 
from  128  in  1901  to  18  in  1908.  Some  of  the  Fourth  of  July 
tetanus  is  believed  to  be  due  to  the  presence  of  the  spores 
in  the  wads  of  blank  cartridges,  and  they  were  demonstrated 
in  them  by  Dolley,^  and  are  said  to  have  been  found  in  car- 
tridges in  Germany  byMusehold  of  Strassburgand  others,  but 
several  other  American  observers  failed  to  find  tetanus  germs 
in  a  total  of  759  cartridges  examined. 

Fomites  and  Anthrax.  —  The  spores  of  anthrax  are  so 
resistant  that  they  have  been  kept  for  ten  or  twelve  years, 
but  the  bacilli  themselves  do  not  survive  any  longer  than 
typhoid  bacilli.  Anthrax,  though  rather  rare  in  the  United 
States  and  England,  is  very  common  in  some  parts  of  the 
world,  particularly  in  Asia,  and  the  spores  are  frequently 
imported  in  dry  animal  products  from  Asiatic  countries. 
Legge*  cites  from  several  observers  who  recovered  the  spores 
from  hair  and  hides  imported  from  China  and  Siberia.  More 
recently  Enrich"'  has  examined  nearly  750  specimens  of  wool, 
hair  and  dust  from  these  materials.     In  over  600  specimens 

'  Tuck,  Jour.  Path.  &  Rac-teriol.,  Edinb.  &  Lond.,  1904,  IX,  38. 

^  Junta  Sup.  de  iSan.  do  la  Isla  do  CJuba,  Supplemento  y  Note  Adi- 
cional,  1902-0;^  -1. 

=•  Dolley,  J.  Am.  M.  Ass.,  ChicaRO,  1905,  XLIV,  466. 

*  LegRo,  Lanw>t,  Loud.,  lOOf),  T,  G94,  and  Rep.  Insp.  of  Fact.,  Lancet, 
Lond.,  1904,  I,  12()(). 

s  Rep.  Antluax  Investigation  Bd.,  Bradford,  Eng.,  No.  3,  1908,  8. 


INFECTION  BY  FOMITES  227 

free  from  blood  he  found  no  anthrax  germs,  but  he  did  find 
them  in  20,  or  14.4,  per  cent,  of  139  bloodstained  specimens. 
These  findings  are  substantiated  in  his  last  report  (1909),  and 
he  speaks  of  a  case  of  anthrax  in  a  man  who  handled  wool 
in  which  anthrax  spores  were  actually  found.  In  64  samples 
of  dust,  anthrax  germs  were  demonstrated  only  once.^  Page^ 
also  gives  references  to  other  similar  findings.  But  such 
observations  are  not  necessary  to  show  that  the  disease  is 
transported  in  this  way,  for  there  is  ample  clinical  evidence 
that  such  goods  are  the  direct  cause  of  anthrax  in  men  and 
animals.  In  fact,  most  industrial  anthrax  in  Western  Europe 
and  North  America  is  caused  by  handling  wool,  hair  and 
hides  imported  from  anthrax-infested  countries. 

Fomites  and  Typhoid  Fever.  —  One  of  the  most  remarkable 
of  the  authenticated  instances  of  fomites  infection  is  the 
transmission  of  typhoid  fever  by  means  of  army  blankets 
from  South  Africa.^  These  blankets  came  from  Africa  in 
October,  1902,  and  were  then  sold.  They  went  to  290 
different  parties.  One  lot  used  on  the  transport  Cornwall 
apparently  gave  rise  to  the  disease  in  May,  1903;  the  use 
of  another  lot  in  England  was  also  followed  by  typhoid 
fever.  Some  of  the  blankets  were  considerably  soiled,  and 
living  bacilli  were  found  on  several  that  were  examined  in 
London. 

Fomites  and  Diphtheria.  —  A  young  man  working  in  a 
laboratory  in  an  American  city  spilled  some  bouillon  culture 
of  diphtheria  bacilli  on  his  coat.  This  coat,  without  disin- 
fection, he  wore  when  calling  on  the  young  woman  to  whom 
he  was  engaged,  and  she  developed  diphtheria  two  days  later. 
The  culture  which  was  spilled  contained  only  the  branching 
forms  of  the  diphtheria  bacillus,  and  the  culture  from  the 
patient's  throat  showed  the  same  forms. 

But  very  few  instances  other  than  the  above  are  on  record 

'  Rep.  of  Chief  Inspector  of  Factories  and  Workshops,  1907,  57. 
2  Page,  J.  Hyg.,  Cambridge,  1909,  IX,  357. 
^  Parkes,  Practitioner,  Lond.,  1903,  LXXI,  297. 


228         THE  SOURCES  AND  MODES  OF  INFECTION 

where  pathogenic  bacteria  have  actually  been  found  on  mate- 
rials which  presumably  have  carried  infection.  According  to 
Simpson,^  plague  bacilli  were  found  by  Kitasato  on  cotton 
goods  imported  into  Japan,  and  this  was  thought  by  Kitasato 
to  be  the  way  in  which  the  disease  was  introduced  into  that 
country,  but  from  what  is  now  known  about  the  mode  of 
extension  of  the  disease  this  seems  highly  improbable. 

Few  Instances  of  Fomites  Infection.  —  But  while  we  may 
admit  that  occasionally  the  virus  of  even  many  of  the  com- 
moner diseases  may  be  retained  on  fomites  for  a  considerable 
length  of  time,  and  ultimately  give  rise  to  new  cases,  there 
is  no  clinical  evidence  to  show  that  such  instances  are  at  all 
common.  Even  when  carefully  sought  for,  fomites  infection 
is  not  very  often  found.  In  my  early  work  as  health  officer 
I  firmly  believed  in  the  importance  of  this  factor,  and  dili- 
gently sought  for  evidence.  The  fact  that  I  found  very  little 
was  one  thing  which  led  to  a  more  careful  consideration  of  the 
subject.  Of  13,970  cases  of  scarlet  fever  reported  in  Michi- 
gan,^ only  335  were  attributed  to  fomites  infection.  To  an 
even  less  degree  are  diphtheria  and  measles  attributed  in 
this  report  to  fomites  infection.  Of  221  cases  of  bubonic 
plague  in  Natal, ^  only  8  were  by  Hill  attributed  to  fomites 
infection,  and  Mitchell  in  Port  Elizabeth  attributed  only 
6  of  337  cases  to  the  same  source.  When  we  consider  that 
most  of  the  evidence  is  extremely  flimsy,  and  that  much  of 
the  alleged  fomites  infection  is  probably  carrier  infection,  and 
remembering  also  how  the  history  of  yellow  fever  has  taught 
us  to  be  wary  of  such  proofs,  we  are  forced  to  the  conclu- 
sion that  there  is  little  in  the  history  of  the  more  prevalent 
infectious  diseases  to  indicate  that  fomites  infection  is  at  all 
common. 

Reasons  for  Belief  in  Fomites.  —  One  reason  why  fomites 
infection  looms  so  large  in  the  minds  of  health  officers,  as 

'  Simpson,  Treatise  on  PiaKne,  Cambridge,  1905,  204. 
'  Rep.  St.  B(l.  Health,  Micii.,  1«)()(),  i;U. 
'  .J.  Ilyg.,  Cambridge,  1907,  Vll,  712. 


INFECTION  BY  FOMITES  229 

well  as  of  the  laity,  is  that  the  striking  character  and  air 
of  raj'stery  about  the  alleged  incidents  are  so  impressive. 
"  Death  in  a  Toy,"  or  "  A  Child  Succumbs  to  the  Dread 
Disease  from  Infection  Lurking  in  its  Mother's  Shawl," 
appeal  to  the  imagination.  That  the  invisible  emanations  of 
disease  should  cling  to  a  garment  for  years  is  too  near  akin 
to  the  stories  of  the  Arabian  Nights  not  to  impress  the  average 
mind.  Hence  it  is  that  the  comparatively  few  instances  of 
real  fomites  infection  have  far  more  than  their  due  weight 
in  our  estimation  of  the  relative  importance  of  different  modes 
of  infection. 

Even  if  all  the  alleged  instances  of  fomites  infection  were 
true,  the  amount  of  disease  apparently  caused  in  this  way 
is  relatively  very  small.  The  frequency  with  which  conta- 
gious disease  can  be  traced  to  fomites  is  not  the  reason  for 
the  general  belief  in  the  importance  of  this  mode  of  infection. 
The  real  reason,  I  have  no  doubt,  is,  that  until  very  recently 
there  seemed  to  be  no  other  way  of  explaining  isolated  cases 
of  disease.  As  a  rule  it  is  impossible,  even  with  modern  aids 
to  the  diagnosis  of  obscure  cases,  to  trace  the  source  of  infec- 
tion of  most  cases  of  contagious  disease,  particularly  in  cities. 
The  theory  of  long  persistent  fomites  infection  seemed  to 
offer  a  reasonable  solution,  and  hence  met  with  universal 
acceptance.  The  theory  was  almost  a  necessity  to  explain 
the  facts  as  they  were  formerly  understood.  Now  we  have 
no  need  for  such  a  theory,  and  a  much  more  satisfactory 
explanation  is  at  hand. 

Evidence  against  Theory.  —  It  is  only  within  a  very  few 
years  that  the  frequency  with  which  mild  atypical  cases  of 
disease  occur  has  been  recognized,  and  the  existence  of 
numerous  entirely  healthy  carriers  is  a  modern  discovery, 
which  is  even  now  denied  by  some.  The  more  carefully 
individual  cases  and  outbreaks  of  disease  are  studied,  the 
more  often  are  they  traced  to  missed  cases  and  carriers. 
It  is  not  probable  that  we  shall  ever  be  able  to  discover  the 
origin  of  all  our  contagious  disease.    We  can  only  infer  its 


230        THE  SOURCES  AXD  MODES  OF  INFECTION 

source  from  the  data  we  have.  As  was  shown  in  the  first 
chapter,  there  is  every  reason  for  thinking  that  disease  germs 
rarely  grow  outside  of  a  hving  body.  Two  other  theories 
are  open  to  us.  Disease  may  be  due  to  the  persistence  of 
infection  on  things,  or  it  may  be  due  to  exposure  to  mild 
cases  or  carriers.  There  should  be  no  hesitancy  in  choosing 
between  the  danger  from  rapidly  dying  germs  on  books, 
money,  furniture  or  clothes,  and  rapidly  growing  germs  in  the 
mouth,  nose  and  intestines  of  persons.  Moreover  things 
must  be  carried,  people  move  freely  at  will. 

If  the  danger  from  fomites  infection  were  as  great  as  is 
generally  believed,  the  contagious  diseases  would  be  much 
more  common  than  they  are.  The  advocates  of  this  theory 
are  constantly  telling  us  how  easily  everything  near  the  sick 
becomes  infected  and  how  long  the  infection  lasts.  Every 
one  knows  that  at  the  best  disinfection  is  imperfect,  and  that 
much  that  passes  for  disinfection  is  no  disinfection  at  all. 
Then  the  missed  cases,  which  all  admit  occur  in  considerable 
numbers,  to  say  nothing  of  the  carriers,  are  constantly  infect- 
ing large  numbers  of  things  which  are  not  subjected  to  any 
disinfection.  Yet  our  scarlet  fever  and  diphtheria  are  not 
increasing,  which  means  that  one  case  of  the  disease  gives  rise 
to  no  more  than  another  case.  If  fomites  infection  occurred 
as  easily  as  is  alk^ged,  each  case  would  ramify  through 
fomites  into  a  dozen  more  cases.  One  reason  for  doubt  about 
the  prevailing  ideas  of  fomites  infection  is  this:  if  fomites 
infection  were  as  common  and  as  easy  as  is  alleged,  few 
could  escape  it,  and  the  infectious  diseases  would  be  much 
more  prevalent  than  they  are.  As  was  shown  in  Chapter  IV, 
the  chances  for  the  transfer  of  fresh  infective  material  are  so 
extremely  numerous  that  there  is  no  necessity  for  assuming 
the  far  more  difficult  and  uncertain  modes  of  aerial  convection 
and  transmission  by  fomites,  and  indeed  there  seems  to  be 
little  f)pportunity  for  their  action. 

Bacteriological  Evidence.  —  Having  considered  some  of 
the  clinical  evidence  of  the  ])art  i)layed  by  fomites  in  the 


INFECTION  BY  FOMITES  231 

transmission  of  infection,  it  is  desirable  to  inquire  what  light 
the  laboratory  study  of  disease  has  thrown  on  the  problem. 
One  of  the  first  labors  of  the  discoverer  of  a  pathogenic  organ- 
ism is  to  determine  its  resistance  to  various  hostile  influences, 
such  as  heat,  cold,  drying,  light  and  disinfectants. 

The  Effect  of  Drying  upon  Bacteria.  ■ —  Drying,  exposure 
to  light  and  lack  of  nourishment  are  the  principal  factors 
which  determine  the  life  of  micro-organisms  on  fomites. 
Besides  the  study  of  the  germs  of  special  disease  by  those 
particularly  interested,  Germano,  whose  work  is  mentioned 
in  the  chapter  on  aerial  infection,  Ficker,^  Zonchello,"  Heim,' 
and  Buckley,^  among  others,  have  given  careful  and  system- 
atic attention  to  the  effect  of  drying  on  the  vitality  of  bac- 
teria. Exceedingl}'  divergent  results  have  been  reported  by 
these  different  observers.  This,  however,  is  not  surprising  if 
the  number  of  factors  involved  is  taken  into  consideration. 
Among  the  most  important  of  these  factors  is  the  amount 
of  light.  Germs  that  are  killed  in  a  few  minutes  in  direct 
sunlight  may  live  for  weeks  in  a  dark  place  or  even  in  diffused 
light.  The  thicker  the  layer  of  infectious  material,  the  longer 
is  its  virulence  likely  to  be  maintained.  This  thickness 
depends  largely  upon  the  nature  of  the  medium.  In  a  dried 
watery  medium,  bacteria  may  die  quickly,  while  they  may 
survive  long  in  sputum  or  feces.  The  more  complete  the 
drying,  the  shorter  the  life,  and  alternate  drying  and  damp- 
ening is  unfavorable.  The  higher  the  temperature,  the 
sooner  the  germs  perish.  Their  vitality  also  varies  with 
the  rapidity  of  the  drying  process  and  the  material  on 
which  they  happen  to  be.  Old  cultures  die  sooner  than 
fresh  ones,  and  different  strains  have  different  powers  of 
resistance.     The  chemical  composition  of  the  medium  and 

1  Ficker,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1908,  LIX,  367. 
»  Zonchello,  Giornale  della  Real  Soc.  Ital.  d'  Igiene,  1905,  XXVII, 
489,  537. 

'  Heim,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1905,  L,  122. 
*  Buckley,  Pub.  Health,  Lond.,  1906-07,  XIX,  290. 


232        THE  SOURCES  AXD  MODES  OF  INFECTION 

the  presence  or  absence  of  other  organisms  may  have  an 
influence. 

The  spores  of  bacteria  are  so  resistant  that  we  should  natu- 
rally expect  the  diseases  caused  by  the  spore-forming  kinds 
to  be  readily  carried  on  fomites.  As  has  been  shown,  this  is 
true  of  anthrax  and  tetanus,  diseases  which  belong  to  this 
class. 

Tjrphoid  Bacilli.  — ■  Among  the  more  hardy  non-spore- 
forming  bacteria  is  the  bacillus  of  typhoid  fever.  In  the  first 
chapter  it  was  shown  that  in  the  presence  of  moisture,  as  in 
privy  vaults,  the  soil,  milk,  water,  etc.,  this  bacillus  some- 
times lives  for  some  months,  though  it  often  dies  out  in  a 
much  shorter  time.  It  remains  to  consider  the  duration  of 
its  life  when  in  a  more  or  less  dry  condition. 

Firth  and  Horrocks^  found  that  typhoid  bacilli  would  live 
on  khaki  for  78  days,  in  feces  dried  on  serge  for  9  to  17  days, 
on  serge  for  10  days  after  it  had  been  exposed  to  direct  sun- 
light for  50  hours.  Pfuhl^  says  that  dried  on  linen  they  lived 
97  days.  Germano^  cites  Gaffky  as  reporting  that  the 
typhoid  bacillus  would  live  for  3  months  when  in  a  dry  con- 
dition, and  that  Uffelmann  recovered  it  from  various  dry 
materials  after  a  period  of  from  21  to  80  days.  But  Germano 
suspects  that  the  substances  were  not  perfectly  dry.  Ger- 
mano himself  was  able  to  preserve  typhoid  bacilli  dried  on 
wood  or  linen  for  90  days,  but  when  he  inoculated  sterile 
dust  with  a  bouillon  culture,  the  bacilli  did  not  survive  over 
4  days  and  sometimes  perished  in  1  day.  Most  of  them 
died  off  very  rapidly.  Buckley  *  found  they  would  live  for 
from  5  days  when  dried  on  paper  in  a  room  to  119  days 
when  kept  on  wood  in  a  moist  chamber.  The  consensus  of 
opinion  seems  to  be  that  while  under  unfavorable  conditions, 

»  Firth  and  Ilorrocks,  Brit.  M.  J.,  Lond.,  1902,  II,  93G,  1094. 
»  Pfuhl,  Ztschr.  f.  HyR.  u.  Infoctionskrankli.,  Loipz.,  1902,  XL,  555. 
'  Gormano,    Ztschr.    f.    Ily^.    u.    Infoctionskrankh.,    Leipz.,    1897, 
XXIV,  40.3. 

'  Buckley,  Pub.  Health,  Loud.,  1906-07,  XIX,  290. 


INFECTION  BY  FOMITES  233 

as  when  quite  dry  and  exposed  to  light,  the  typhoid  bacillus 
may  die  in  a  few  days,  yet  under  conditions  which  must  fre- 
quently prevail  it  may  remain  alive  on  such  things  as  cloth- 
ing and  bedding  for  some  months. 

Mediterranean  Fever.  —  The  micrococcus  of  Mediterra- 
nean fever  has  about  the  same  resistance  as  that  of  typhoid 
fever.  Like  the  typhoid  bacillus,  it  is  killed  in  an  hour  or 
two  in  direct  sunlight.  Dried  on  glass  it  survives  16  days,  in 
moist  soil  72  days  and  on  a  blanket  80  days.^ 

Diphtheria.  —  Loeffler  kept  dry  diphtheria  bacilli  alive  for 
from  9  to  16  weeks,  Roux  and  Yersin  for  5  months,  D'Espine 
and  Morignac  for  between  3  and  4  months,  and  Park  for  4 
months.^  Germano^  found  that  they  would  retain  their 
virulence  after  remaining  in  dry  earth  or  dust  for  20  to  40 
days,  and  Reyes  ^  found  them  virulent  in  sand  and  on  cloth 
after  14  days.  Buckley^  recovered  living  bacilli,  when  dried 
in  the  air  on  paper,  after  6  days,  on  wood  after  8  days,  on 
cotton  and  on  glass  after  24  days,  and  on  plaster  after  37 
days.  Hill  **  exposed  to  ordinary  room  conditions,  glass  rods 
which  had  been  rubbed  on  a  culture  of  diphtheria  bacilli. 
Of  these  28  per  cent  survived  14  days  and  9  per  cent  20 
days.  Houston  ^  found  that  they  died  very  quickly  in  earth. 
Leighton^  recovered  them  from  warm  moist  modeling  clay 
up  to  18  days.  Williams  ®  could  not  recover  the  germs 
after  24  hours  from  pencils  moistened  by  the  lips  of  patients 
who  had  the  bacilli  in  the  throat. 

1  Horrocks,  Rep.  Commission  Roy.  Soc,  Pt.  I,  1901. 
^  Cited  by  Germane. 

^  Germane,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1897, 
XXV,  439. 

*  Reyes,  Jahrb.  u.  d.  Fortschr.  .  .  .  d.  path,  mik.,  Baumgarten, 
1895,  XI,  203. 

5  Buckley,  Pub.  Health,  Lond.,  1906-07,  290. 

'  Hill,  Am.  Pub.  Health  Ass.  Rep.,  1902,  XXVIII,  209. 

'  Houston,  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  Lond.,  1898-99,  XXXIII,  413. 

*  Leighton,  Pediatrics,  1901,  XII,  360. 

«  Williams,  N.  Y.  Health  Dept.,  Sci.  Bull.  2,  1895,  16. 


234         THE  SOURCES  AND  MODES  OF  INFECTION 

Dysentery  Bacilli.  —  According  to  Pfuhl  ^  the  bacillus  of 
dysentery  may  remain  alive  for  17  days  when  dried  on  cloth, 
or  10  days  when  in  dry  sand.  In  direct  sunlight  it  dies  in  30 
minutes.^  Kruse^  claims  that  when  dry  it  will  retain  its  vital- 
ity for  months. 

Tubercle  Bacilli.  —  More  attention  has  been  paid  to  the 
vitality  of  the  tubercle  bacillus  than  to  that  of  other  bacteria. 
It  is  generally  believed  to  be  one  of  the  most  resistant,  but 
Hill  *  has  shown  that  under  the  same  natural  conditions  of 
dryness,  light,  etc.,  the  diphtheria  bacillus  will  outlive  it. 
Many  of  the  earlier  writers  claimed  a  very  considerable  lon- 
gevity for  the  tubercle  bacilli  in  dried  sputum.  Villemin, 
Schill,  Fischer,  Koch,  De  Thoma,  Sormani,  Maffuci  and 
Cadeac  and  Malet  claimed  a  life  of  from  1  to  9  months.^ 
Ransome  and  Delepine  ^'  found  that  the  bacilli  if  exposed  to  air 
and  light  would  not  survive  45  days,  but  if  kept  in  dim  light 
they  did  survive.  TwichelF  placed  sputum  in  a  folded  hand- 
kerchief, in  a  folded  carpet,  and  spread  on  wood,  and  ex- 
posed it  to  the  air  at  ordinary  temperatures  and  in  diffused 
light.  The  bacilli  survived  for  39  to  70  days.  In  sunhght 
they  died  in  a  few  hours.  Migneco  ^  found  that  when  dried 
on  cloth  in  the  sun  they  lived  from  20  to  30  hours. 

Not  so  Resistant  as  Believed.  —  Many  recent  observers 
do  not  find  this  bacillus  so  resistant  as  has  been  supposed. 
That  it  perishes  in  direct  sunlight  in  loss  than  an  hour  seems 
certain.  Weinzirl,^  using  improved  methods,  finds  that  it 
will  not  survive  10  minutes,  and  frequently  dies  in  2  minutes. 

'  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Lcipz.,  1902,  XL,  555. 
»  Shiga,  Deutsche  mcd.  Wchnschr.,  1901,  XXVII,  765,  783. 
»  Kruse,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  370,  386. 

*  Hill,  Am.  Pub.  Health  Ass.  Rep.,  1902,  XXVII,  209. 

*  KoUe  and  Wasserman's  Handhucih  [etc.],  Jena,  1903,  II,  108. 

•  Ransome  and  Delepine,  Proceedings  Royal  Society,  No.  336. 
'  Twichell,  Med.  News,  N.  Y.,  1905,  LXXXVII,  642. 

«  Migneco,  Arch,  of  Hyg.,  Miinchen  u.  Leipz.,  1895,  XXV,  361. 

•  Weinzirl,  J.  Infect.  Dis.,  Chicago,  1907  [Suppl.  No.  3],  128. 


I 


INFECTION  BY  FOMITES  235 

Caddac  ^  spread  sputum  on  marble  and  could  find  no  living 
germs  after  the  fourteenth  day.  On  a  porous  plaster  plate 
they  died  within  2  days.  Hill "  dried  sputum  on  glass  rods 
in  the  air  under  ordinar}-  room  conditions,  and  found  no  liv- 
ing bacilli  at  the  time  of  his  first  test,  which  w^as  made  after 
16  days.  Rickards,  Slack  and  Arms^  have  made  verj^  careful 
tests  by  exposing  sputum  on  wood  and  cloth  in  the  rooms  of 
ordinary  tenements.  They  find  that  when  dry  and  kept  in 
diffused  light  the  bacilli  will  live  about  1  month,  in  dark  and 
dry  rooms  up  to  85  days;  another  strain  survived  only  45 
days  under  the  latter  conditions.  Rosenau*  says  that  further 
work  upon  the  viability  of  the  dried  tubercle  bacillus  may 
change  our  views  as  to  its  hardiness,  and  failure  to  recognize 
lesions  produced  by  the  dead  bacillus  is  responsible  for  some 
of  the  false  conclusions  reached  by  certain  experimenters. 

Plague  Bacilli.  —  Simpson  ^  states  that  the  German  Plague 
Commission  found  that  in  a  large  number  of  experiments  with 
sputum,  blood,  etc.,  dried  on  all  sorts  of  materials,  under 
natural  conditions,  the  bacilli  of  bubonic  plague  do  not  sur- 
vive over  8  days.  Of  many  specimens  of  the  organism  dried 
on  cover  glasses  and  sent  to  England,  none  survived  the 
journey.  Kitasato^  found  that  plague  pus  dried  on  cover 
glasses  lost  its  virulence,  when  exposed  to  the  sun,  in  from 
3  to  4  hours,  and  this  has  been  substantiated  by  others.  As 
was  referred  to  in  the  first  chapter,  the  work  of  the  last  Eng- 
lish Plague  Commission  shows  that  virulent  plague  bacilli 
cannot  be  found  in  the  dirt  floors  of  native  houses  after  48 
hours.     According  to  the  careful  experiments  of  Buckley,^ 

'  Cadeac,  Lyon  med.,  1905,  CV,  865,  Abst.  Brit.  M.  J.,  Lond., 
1906,  I. 

'  Hill,  Am.  Pub.  Health  Ass.  Rep.,  1902,  XXVIII,  209. 

'  Rickards,  Slack  and  Arms,  Am.  J.  Pub.  Hyg.,  Bost.,  1909,  V,  586. 

*  Rosenau,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 
No.  57,  1909. 

*  Simpson,  Treatise  on  Plague,  Cambridge,  1905,  96. 
«  Kitasato,  Lancet,  Lond.,  1894,  II,  428. 

'  Buckley,  Pub.  Health,  Lond.,  1906-07,  XIX,  290. 


236        THE  SOURCES  AND  MODES  OF  INFECTION 

plague  bacilli  remain  alive  after  drying  in  the  air,  for  11  hours 
when  dried  on  cotton,  2  hours  on  wood,  5  hours  on  plaster, 
2  hours  on  glass,  and  3  hours  on  paper.  When  kept  in  a 
desiccator  they  survived  on  cotton  for  22  hours,  and  in  a 
moist  chamber  for  only  36  hours.  Gotschlich,^  by  folding 
material  containing  the  germs  in  cloth,  could  preserve  them 
alive  for  from  3  to  4  weeks.  Simpson^  reports  that  infected 
cloth  may  retain  its  virulence  for  80  days.  According  to 
Verjbitski,^  the  crushed  viscera  of  experimental  animals  and 
the  crushed  bodies  of  fleas  when  smeared  on  cloth  and  dried 
will  preserve  the  bacilli  alive  for  130  days  at  a  temperature 
of  4-5°  C,  and  for  35  days  at  room  temperature.  Bandi  and 
Stagnitta-Balistreri  state  that  these  bacilli  may  survive  in  the 
bodies  of  dead  rats  for  2  months.  The  vitality  of  the  plague 
bacillus  has  been  carefully  investigated  by  Rosenau,^  who 
does  not  consider  it  a  frail  organism.  Temperature  is  the 
most  important  factor  in  its  life.  It  may  lose  its  virulence 
before  it  loses  its  vegetability.  It  dies  in  a  few  days  on  the 
dry  surface  of  hard  objects  and  on  paper.  Rosenau  says  that 
bedding  may  harbor  the  infection  for  a  long  time.  Tidswell,^ 
experimenting  with  a  large  number  of  materials,  found  that 
plague  bacilli  dried  under  natural  conditions  lived  only 
from  3  to  4  days,  but  when  dried  slowlj''  on  muslin  they 
might  live  for  21  days.  The  colder  the  climate  the  greater 
is  the  chance  of  the  persistence  of  infection.  In  this  all  are 
agreed. 

Pus-forming  Bacteria. — The  pus-forming  bacteria  are  quite 
resistant  to  drying.     According  to  Germano,"  streptococcus 

*  Gotschlich,   cited  by  Kolle  and  Wasserman's  Handbuch  [etc.], 
Jena,  1903,  II,  496. 

^  Simpson,  Treatise^  on  Plague,  (.'anibnd}2;e,  1905,  93. 
^  Verjbitski,  J.  Hyg.,  Cambridge,  1908,  203. 

*  Rosenau,  U.  S.  Pub.  Health  and  Mar.  Hcsp.  Serv.  Hyg.  Lab.  Bull. 
No.  4,  1901. 

^  Tid.svvell,  I{('f)ort  on  Plague  in  Sydney,  J.  A.  Thompfson,  1902,  67. 
"  Germano,  Ztschr.  f.  Ilyg.  u.  Infectionskrankh.,  Leipz.,  1897,  XXVI, 
66. 


INFECTION  BY  FOMITES  237 

withstands  drying  for  a  month,  but  different  strains  have 
varying  degrees  of  resistance.  See  also  Heim^  and  Neisser,^ 
who  found  that  these  organisms  would  withstand  drying  for 
a  long  time.  Buckley^  could  keep  staphylococcus  alive  for 
only  7  days  when  on  paper  in  the  air,  and  on  other  sub- 
stances and  under  different  conditions  for  varying  times,  up 
to  130  days  on  cotton  kept  in  a  desiccator. 

Cholera  Spirilla.  —  Germano^  in  a  number  of  experiments 
found  that  the  cholera  spirillum  in  dried  feces  lived  only  3 
days  and  in  other  experiments  only  1  day.  He  also  cites  Zon- 
chello  as  reporting  that  it  is  among  the  least  resistant  bac- 
teria. Kitasato''  states  that  it  may  retain  its  virulence  up 
to  8  days,  but  that  it  may  die  sooner,  especially  when  dried  on 
glass.  Usually  it  lives  from  a  few  hours  up  to  4  days.  Koch 
and  Gaffky^  state  that  when  dried  on  glass  it  survives  only 
a  few  hours,  but  when  dried  on  fabrics  it  may  retain  its  viru- 
lence up  to  4  days.  Buckley^  found  that  cholera  germs  would 
survive  when  dried  in  the  air,  9  hours  on  cotton,  8  hours  on 
wood.  If  hours  on  glass,  and  5  hours  on  paper.  They  did 
not  survive  nearly  so  long  when  dried  in  a  desiccator.  This 
is  contrary  to  the  experience  of  others,  for  as  a  rule  bacteria 
live  much  longer  when  dried  in  a  desiccator  than  when  dried 
in  the  open  air  under  natural  conditions.  Gotschlich^  says 
that  cholera  germs  will  Hve  in  dejecta  dried  in  the  air  on 
clothing  for  36  days,  and  when  damp,  according  to  Karl- 
niski's  observations,  for  7  months.  He  considers  that  such  a 
long  life  is  exceptional,  and  that  generally  the  spirillum  dies 
in  a  few  days.    A  duration  of  only  a  few  days,  or  even  hours, 

1  Heim,  Ztsch.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1905,  L,  122. 

*  Neisser,  Ueber  Luftstaub-Infection,  Inaug.  Dis.,  Breslau,  1898. 
3  Buckley,  Pub.  Health,  Lond.,  1896-97,  XIX,  290. 

*  Germane,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1897, 
XXIV,  403. 

°  Kitasato,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1885,  V,  134. 
^  Koch,  Arb.  a.  d.  k.  Gesundsamte,  Berl.,  1886,  I,  199. 
'  Gotschlich,  KoUe  and  Wasserman's  Handbuch  [etc.],  Jena,  1902, 
I,  211. 


238        THE  SOURCES  AND  MODES  OF  INFECTION 

was  also  found  by  Gamaleia/  Hesse  ^  and  Koch  and 
Gaffky. 

Pneumococci.  —  The  pneumococcus  is  widely  distributed 
in  health}'  human  mouths,  and  the  opportunities  for  the 
direct  transference  of  fresh  secretion  are  so  numerous  that 
it  probably  is  of  no  importance  whether  this  organism  lives 
long  or  not.  Wood^  found  that  while  pulverized  sputum  lost 
its  virulence  in  a  few  hours  when  dried  in  mass,  it  might, 
under  favorable  conditions, retain  it  35  days.  Buerger*  recov- 
ered the  pneumococci  from  a  handkerchief  7  days  after  it  had 
been  in  use.  Germane^  and  some  others  claim  a  consider- 
ably greater  resistance.  Germano  kept  it  alive  in  dust  for 
140  days,  but  the  tendency  of  later  observers  is  to  consider 
it  a  much  feebler  organism. 

Influenza  Bacilli.  —  According  to  Pfeiffer,^  the  influenza 
bacillus  retains  its  vitality  when  dried  in  sputum  for  36  to  40 
hours.  When  dried  on  a  cover  glass  and  kept  at  37°  C.,  it 
survives  for  only  2  hours,  and  when  kept  at  room  temperature 
for  from  8  to  20  hours. 

Meningococci.  —  The  evidence  in  regard  to  the  germ  of 
cerebro-spinal  meningitis  appears  to  be  somewhat  conflicting. 
Germano  and  Neisser  claim  considerable  resistance  for  it,  as 
also  does  Jaeger.^  Germano  said  it  would  live  for  80  to  90 
days,  but  it  is  said  that  he  did  not  work  with  the  true  menin- 
gococcus.® More  careful  and  recent  observers  do  not  find  it 
so  resistant.     Councilman  ®  found  that  it  would  live  when  dry 

*  Gamaleia,  Deutsche  med.  Wchnschr.,  1893,  XIX,  1350. 

*  Hesse,  Ztschr.  f.  Hyg.  u.  Infec^tionskrankh.,  Leipz.,  1893,  XIV,  30. 
3  Wood,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  592. 

*  Buerger,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  518. 

^  Germano,  Ztschr.  f .  Hyg.  u.  Infectionskrankh.,  Leipz.,  1897,  XXVI,  66. 

'  Pfeiffer,  Nothnagel'a  Encycl.  Pract.  Med.,  Phila.  and  Load.,  Influ- 
enza, 1895,  584. 

'  Jaeger,  Med.  Klin.,  Berl.,  1905,  I,  990,  1011. 

«  Arkwright,  J.  Hyg.,  Cambridge,  1907,  VII,  193. 

"  Special  Ileport  on  Cerebro-spinal  Meningitis,  Mass.  St.  Bd. 
Health,  1898,  78. 


INFECTION  BY  FOMITES  239 

in  a  dark  room  less  than  72  hours.  Albrecht  and  Ghon  ^ 
could  keep  it  only  24  hours  in  the  dark,  and  Bettencourt  and 
Franca  -  less  than  9  hours.  Kache,^  Kutscher  *  and  Fliigge  ^ 
had  similar  results,  and  Arkwright  ^  succeeded  in  keeping 
the  organism  alive  only  from  20  to  48  hours.  Lingelsheim  ^ 
says  that  in  culture  media  it  dies  in  a  few  hours,  but  in 
sputum  it  may  be  kept  alive  for  5  days. 

Gonococci.  —  According  to  Schaffer  and  Steinschneider,^ 
and  Ullmann  ^  the  gonococcus  lives  only  a  few  hours  on 
textiles,  at  most  36  hours,  and  often  dies  as  soon  as  thor- 
oughly dry. 

Hertmanni  ^^  from  his  own  observations  and  those  of 
others,  whom  he  cites,  concludes  that  the  Tryponema  -pal- 
lida of  syphilis  may  retain  its  motility  for  some  months  if 
left  moist  and  in  the  dark.     Drying  quickly  kills  it. 

Bacteria  on  Fomites.  —  Pathogenic  bacteria  have  fre- 
quently been  sought  for  on  various  articles  believed  to  be 
likely  to  be  the  means  of  transporting  disease,  but  with  the 
exception  of  the  spores  of  anthrax  and  tetanus  they  have 
rarely  been  found.  The  finding  of  anthrax  and  tetanus  spores 
has  already  been  referred  to.  Besides  the  places  mentioned, 
tetanus  germs  have  been  found  in  the  soil  in  various  places, 
in  the  dirt  filling  between  the  floors  of  houses  ^^  and  in  one 

1  Albrecht  and  Ghon,  Wien.  klin.  Wchnschr.,  1901,  XIV,  984. 
^  Bettencourt  and  Franca,   Ztschr.   f.    Hyg.   u.   Infectionskrankh., 
Leipz.,  1904,  XLVI,  463. 
'  Cited  by  FUigge. 
«  Kutscher,  Deutsche  med.  Wchnschr.,  1906,  XXXII,  1071. 

5  Flugge,  Khn.  Jahrb.,  Jena,  1905,  XV,  373. 

6  Arkwright,  J.  Hyg.,  Cambridge,  1907,  VII,  193. 

'  Lingelsheim,  Khn.  Jahrb.,  Jena,  1905,  XV,  373;  Ztschr.  f.  Hyg.  u. 
Infectionskrankh.,  Leipz.,  1908,  LIX,  457. 

8  Verhandl.  d.  IV  Kong.  d.  deutsch.  dermatol.  Gesellsch.,  Breslau, 
1904. 

9  Ullmann,  Wien.  med.  Blatter,  1897,  XX,  703  et  seq. 
1"  Hertmanni  Dermat.  Ztschr.,  Berl.,  1909,  XVI,  633. 

"  Heinzelmann,  Munchen  med.  Wchnschr.,  1891,  XXXVIII,  185, 
200. 


240        THE  SOURCES  AND  MODES  OF  INFECTION 

instance  in  a  house  where  there  had  been  a  death  from 
tetanus/ 

Distribution  of  Germs  of  Suppuration.  —  The  pus  organ- 
isms are  quite  resistant  to  drying,  and  if  they  were  not,  they 
are  so  widely  distributed,  being  found  constantly  on  the  skin 
and  mucous  surfaces  of  human  beings,  that  their  presence 
might  be  expected  wherever  human  beings  are  found.  They 
have  as  a  matter  of  fact  been  found  almost  wherever  sought, 
as  on  clothing,  books,  money,  instruments,  floors  and  wood- 
work, and  indeed  on  anything  that  is  touched  by  the  hand 
of  man. 

Diphtheria  Bacilli  on  Fomites.  —  Diphtheria  bacilli  have 
been  frequently  searched  for  on  all  kinds  of  objects  and  fre- 
quently found.  AbeP  and  Wesbrook^  found  them  on  toys, 
and  in  Abel's  case  it  was  86  days  after  infection.  Trevelyan* 
recovered  them  from  a  handkerchief  1 1  weeks  after  it  had  been 
used  by  a  diphtheria  patient.  Park^  took  cultures  which 
proved  positive  in  almost  every  instance,  from  dried  stains  on 
bedclothing  soiled  by  children  sick  with  diphtheria.  He  also 
found  the  bacilli  alive  in  a  piece  of  membrane  after  4  months. 
Wright  and  Emerson "  made  20  cultures  from  various  articles 
in  the  Boston  City  Hospital,  and  found  5  positive.  Of  these 
3  were  from  the  shoes,  1  from  the  hair  of  an  attendant,  and 

1  from  a  floor  brush.  Schumburg^  in  40  cultures  from  a 
room  occupied  by  a  diphtheria  patient  recovered  virulent 
bacilli  from  a  drinking  glass  and  the  handle  of  a  mirror.    In 

2  of  the  5  cultures  the  virulence  of  the  organism  was  low. 

1  Gotschlich,  Kollo  u.  Wasserman's  Handbuch  [etc.],  Jena,  1902, 1,  210. 

2  Abel,  Ceritralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jona,  1892,  XIV, 
756. 

'  Wesbrook,  Wilson  and  McDanicl,  Am.  Pub.  Health  Ass.  Rep., 
1899,  XXV,  .546. 

*  Trevelyan,  Lancet,  Lond.,  1900,  I,  1443. 

">  Park,  Med.  Rec,  N.  Y.,  1892,  XLII,  116. 

*  Wright  and  Emerson,  Centralbl.  f.  liakteriol.  [etc.],  I  Abt.  Orig., 
Jena,  1894,  XVI,  412. 

'  Sclnmiburg,  Ztschr.  f.  iirztl.  Fortbild.,  Jena,  1905,  II,  567. 


INFECTION  BY  FOMITES  241 

Weichardt^  took  300  swabbings  from  various  things  in  a 
sick-room  and  250  from  other  parts  of  the  house,  and  found 
diphtheria  germs  3  times  on  objects  which  had  been  in  contact 
witli  the  patient's  mouth.  HilP  took  532  swabbings  from  a 
room  occupied  by  a  diphtheria  patient,  and  obtained  4  posi- 
tive results,  all  of  which  were  from  objects  handled  by  the 
patient.  In  Providence  about  200  swabbings  taken  under 
similar  circumstances  showed  no  diphtheria  bacilli.  These 
last  three  observations  indicate  that  diphtheria  bacilli  are 
not  very  numerous,  even  on  objects  brought  into  close  con- 
tact with  the  patient.  Kober'  could  find  no  bacilli  on  the 
floor,  bed  linen,  etc.,  of  10  houses  in  which  there  had  been 
diphtheria,  and  he  states  that  Heymann  did  not  find  them 
in  the  Hygienic  Institute  at  Breslau.  Klein  could  not  find 
them  on  telephones  in  London,^  and  Hill  in  Boston^  could 
not  find  them  on  24  mouthpieces  of  lung-testing  machines. 

Tubercle  Bacilli  on  Fomites.  —  While  the  tubercle  bacillus 
is  not  so  resistant  to  drying  as  was  formerly  thought,  it  is 
discharged  in  such  numbers  in  the  sputum  that  it  has  been 
found  outside  of  the  body  more  often  than  have  any  other 
organisms  except  the  pus-forming  bacteria.  Reference  to 
finding  it  in  dust  will  be  given  in  the  next  chapter.  When 
in  considerable  masses  of  sputum,  and  kept  damp,  the  bacillus 
will  survive  longer  than  when  mixed  with  dust.  Besides  on  the 
floors  and  various  articles  in  rooms,  the  bacillus  has  been 
found  in  books  which  were  in  use  for  some  years  in  a  circu- 
lating library."  Petersson^  examined  the  history  charts  kept 
by  the  bedside  of  tuberculous  patients  and  put  away  for 

1  Weichardt,  Jahresb.  u.  d.  Fortschr.  .  .  .  d.  path.  Mik.,  Baum- 
garten,  1900,  XVI,  197. 

2  Hill,  Am  Pub.  Health  Ass.  Rep.,  1902,  XXVUI,  209. 

'  Kober,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899, XXXI, 449. 
'  Klein,  Abst.  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  1866. 
*  Hill,  Rep.  Bd.  Health,  Boston,  1906,  91. 

®  Mitulescu,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1903, 
XLIV,  397. 

'  Petersson,  Ztschr.  f.  klin.  Med.,  Berl.,  1907,  LXIII,  346. 


242        THE  SOURCES  AXD  MODES  OF  INFECTION 

periods  varying  from  months  to  years.  He  found  by  micro- 
scopic examination  tubercle  bacilli  on  two  books  that  were 
kept  for  six  years.  Bissell  ^  washed  the  pockets  of  some  uni- 
forms that  had  been  used  by  soldiers  sick  with  consumption, 
and  obtained  two  positive  results  by  guinea-pig  inoculation. 
Friberger  ^  used  a  vacuum  cleaner  to  remove  the  dirt  from 
clothing  fresh  from  use  by  tuberculous  patients,  and  found 
virulent  bacilli  in  3  of  12  tests. 

Cholera  Spirilla.  —  Although  the  life  of  the  cholera  spiril- 
lum outside  of  the  body  appears  to  be  short,  usually  only  a 
few  days  and  often  less,  some  early  observers,  as  Babes, ^  claim 
to  have  found  it  on  the  personal  effects  of  cholera  patients. 

Resistance  of  Protozoa.  —  There  is  no  theoretical  reason 
why  the  protozoan  blood  parasites  might  not,  in  a  spore-like, 
resistant  stage,  withstand  drying  and  remain  alive  for  some 
time  outside  of  the  body.  But  there  is  no  experimental  evi- 
dence to  show  that  in  any  of  the  well-known  protozoan  dis- 
eases such  spores  are  formed.  There  is  certainly  no  clinical 
evidence  to  show  that  such  diseases  are  ever  carried  on 
fomites,  and  for  malaria,  yellow  fever,  sleeping  sickness  and 
Texas  cattle  fever  there  is  convincing  evidence  that  they 
are  not  so  carried. 

Resistance  of  Vaccine  Virus.  —  With  two  exceptions,  prac- 
tically no  experimental  work  has  been  done  with  the  virus 
of  any  of  the  infectious  diseases,  a  specific  organism  for  which 
has  not  been  determined.  Vaccine  virus  has  an  extensive 
use,  and  it  is  desirable  to  store  it  and  transport  it  long  dis- 
tances, so  that  its  keeping  qualities  have  received  considerable 
attention.  When  the  infectious  material  dries  naturally  in 
the  crust  which  forms  from  the  vesicle,  it  retains  its  virulence 
for  a  considerabk;  time.     These  crusts  were  largely  used  in 

'  Rissoll,  Mod.  News,  N.  Y.,  1899,  LXXIV,  156. 

'  Friherser,  Ztsclir.  f.  Tiiberk.  u.  ITeilstaltonw.,  Leipz.,  1908-09,  XIII, 
37. 

'  Shakespeare,  K('f)ort  on  Cliok^ra  in  Europe  and  India,  U.  S.  Gov. 
Print.  Off.,  1890,  GOG. 


INFECTION  BY  FOMITES  243 

Providence  for  maintaining  the  Jennerian  strain  of  vaccine, 
which  was  used  in  the  health  department  for  nearly  fifty 
years.  The  crusts,  when  taken  from  the  arm  and  kept 
wrapped  in  paper  in  a  dark  place,  could  be  relied  upon  to 
retain  their  virulence  for  a  month,  and  often  did  retain  it 
longer.  When  kept  in  a  tightly  corked  bottle  in  a  refrigerator, 
they  will  generally  remain  virulent  over  6  months.  If  exposed 
to  light  and  air  and  varying  temperature,  the  virulence  may 
be  lost  in  less  than  a  month.  A  thin  layer  of  the  same  lymph 
on  a  quill  does  not  remain  active  when  exposed  to  the  air 
for  more  than  a  week  or  ten  days.  The  ivory  points  covered 
with  vaccine  matter,  which  were  so  much  used  a  few  years 
ago,  were  usually  guaranteed  to  keep  3  weeks,  and  often  did 
remain  virulent  a  month  or  more.  But  there  was  usually 
more  than  one  layer,  and  the  thickness  of  the  material  was 
further  increased  by  the  presence  of  blood  and  leucocytes. 
According  to  Seaton,^  dried  vaccine  matter  on  points  may 
keep  for  from  6  or  9  months  or  more,  and  he  quotes  Husband 
as  securing  successful  vaccinations  from  7  of  93  dried  points 
kept  for  periods  varying  from  6  to  30  months.  Vaccine  matter 
in  powder  also  has  been  kept  by  Warlomont  and  others  for 
several  months.^  Recently  Green  ^  has  kept  dried  pulverized 
vaccine  matter  in  sealed  tubes  for  periods  varying  from  20 
days  at  37°  C.  to  252  days  at  10-15°  C.  and  301  days  at 
4°  C.  Although  under  exceptional  circumstances  dried  vac- 
cine matter  may  be  kept  a  considerable  time,  it  requires  great 
care  and  often  results  in  failure.  Hence  early  in  the  nine- 
teenth century,  in  order  to  introduce  vaccination  into  her 
American  possessions,  the  Spanish  Government*  sent  out  a 
ship  with  a  number  of  children  on  board,  so  that  by  successive 
arm-to-arm  vaccinations  fresh  lymph  might  be  carried  across 
the  seas.    At  the  end  of  the  nineteenth  century,  when  Porto 

^  Seaton,  Handbook  of  Vaccination,  1868,  172. 

*  Warlomont,  Manual  of  Animal  Vaccination,  Phila.,  1886,  139. 
»  Green,  J.  Hyg.,  Cambridge,  1908,  VIII,  528. 

*  Life  of  Jenner,  Baron,  I,  606;  II,  78. 


244         THE  SOURCES  AND  MODES  OE  IXFECTION 

Rico  came  under  the  control  of  the  United  States,  the  diffi- 
culty of  transporting  vaccine  virus  to  the  island  became  so 
great,  so  little  active  virus  surviving  even  this  short  voyage, 
that  it  was  necessary  to  establish  a  vaccine  farm  on  the  island. 
In  the  Philippine  Islands  it  was  found  to  be  necessary  to 
transport  the  virus  packed  in  ice  to  inland  villages.^ 

Resistance  of  Smallpox  Virus. — It  is  a  common  belief  that 
the  crusts  in  variola  are  infectious,  and  they  are  supposed  to 
have  been  used  at  times  in  the  practice  of  inoculation.  I  do 
not  remember  to  have  seen  any  evidence  of  this  till  I  came 
across  the  work  of  Brinckerhoff.^  He  refers  to  a  rather  limited 
literature,  and  details  his  own  experiments,  which  determined 
a  persistence  of  virulence  in  the  crusts  for  periods  of  from  22 
to  52  days,  and  in  one  instance  to  88  days. 

Comparative  Resistance.  —  Experiment  shows  that  some 
pathogenic  organisms,  like  those  of  gonorrhea  and  cerebro- 
spinal meningitis,  are  of  such  feeble  resistance  that  infection 
by  fomites,  as  ordinarily  understood,  is  in  these  diseases  highly 
improbable.  It  is  also  shown  that  certain  other  bacteria,  as 
those  of  diplftheria,  typhoid  fever  and  tuberculosis,  are  resist- 
ant enough  to  make  infection  by  fomites  very  possible.  But 
it  appears  that  all  known  pathogens,  except  those  having 
spores,  tend  to  die  off  quite  rapidly  outside  of  the  body,  and 
that  under  natural  conditions  it  is  rather  the  exception  for 
them  to  persist  for  any  great  length  of  time.  It  is  worth 
noting  that  the  typhoid  bacillus  is  more  resistant  than  any 
other  pathogenic  organism  referred  to.  Yet  we  hear  almost 
nothing  about  fomites  infection  in  that  disease.  Is  it  not 
because  attention  has  been  directed  to  other  sources  which 
have  been  believed  to  be  sufficient,  so  that  there  has  been 
little  temptation  to  assume  inf(>ction  by  fomites  ?  Infection 
by  fomites  has,  on  the  other  hand,  been  considered  of  much 
importanc(^  in  cholera,  the  spirillum  of  which  is  far  less  resist- 
ant than  is  the  bacillus  of  typhoid  fever,  probably  because 

»  Rep.  \V\.  Iloalth,  Philippine  Isl.,  1904-05,  23. 

«  Brlnckerhoff,  J.  Med.  Research,  Host.,  1904,  XI,  284. 


INFECTION  BY  FOMITES  245 

in  the  absence  of  the  knowledge  of  carriers  which  we  now 
possess  the  world-wide  diffusion  of  this  disease  seemed  inex- 
plicable except  by  means  of  fomites. 

Experiments  with  Yellow  Fever.  —  With  a  few  notable 
exceptions,  little  experimental  work  has  been  done  to  deter- 
mine the  part  played  by  fomites  in  the  spread  of  disease. 
When  Reed,  Carroll  Lazear  and  Agramonte  proved  that  yel- 
low fever  is  transmitted  by  the  mosquito,  it  still  remained 
uncertain  whether  it  might  not  also  be  carried  in  other  ways, 
and  sanitary  officials  were  generally  so  convinced  of  the  over- 
whelming evidence  of  the  great  part  played  by  fomites,  that 
definite  proof  or  disproof  of  the  fact  was  earnestly  desired. 
The  complete  failure  of  the  commission  to  produce  the  disease 
in  human  beings  by  fomites  is  well  known,  and  their  experi- 
mental work  has  now  been  corroborated  by  abundant  clinical 
evidence  from  all  the  great  endemic  foci  of  this  disease.  In 
these  experiments,  non-immunes  were  confined  in  a  small 
room  for  a  number  of  days  in  close  contact  with  bedding  and 
clothing  fresh  from  yellow-fever  cases,  most  of  which  was 
soiled  with  excreta  and  vomitus.^  The  experiments  were 
repeated  a  number  of  times,  but  in  no  instance  did  the  disease 
develop.  When  not  long  after  I  stood  in  one  of  those  dirty 
little  rooms  in  company  with  Dr.  Finlay  and  Dr.  Gorgas,  and 
saw  some  of  the  old  bedding  lying  in  the  corner,  I  reaUzed 
as  never  before  how  very  much  greater  are  the  difficulties  in 
observation  than  in  experiment,  and  it  seemed  that  the  time 
had  come  when  the  prevailing  views  as  to  the  importance  of 
fomites  infection  in  other  diseases  than  yellow  fever  should 
be  seriously  reviewed. 

Observations  on  Plague.  —  In  another  disease,  bubonic 
plague,  exceptionally  brilliant  work,  from  the  purely  epidemi- 
ological standpoint,  has  been  done  by  Thompson  in  Australia. 
It  is  true  enough  that  conditions  are  much  more  favorable  for 
observation  when  a  disease  first  invades  a  country  than  when 
it  has  become  as  widespread  as  plague  is  in  India,  but  in  no 
1  Phila.  M.  J.,  1900,  VI,  790. 


246        THE  SOURCES  AND  MODES  OF  INFECTION 

place  have  they  been  taken  advantage  of  as  they  were  in 
Sydney.  Thompson  '  showed  conclusively  that  rat  plague 
preceded  human  plague,  that  the  flea  was  the  intermediary 
between  rat  and  man,  and  that  in  New  South  Wales,  at  least, 
fomites  had  no  part  in  the  diffusion  of  the  disease.  These 
observations  have  been  confirmed  in  other  parts  of  Australia.' 
Experiments  with  Plague.  —  The  present  English  Plague 
Commission  have,  by  their  ingenious  and  painstaking  ex- 
periments and  observations  in  India,  confirmed  Thompson's 
work.  Reference  will  be  made  in  another  chapter  to  the 
experiments  on  the  transmission  of  the  disease  by  the  air,  in 
which  they  definitely  proved  that  aerial  infection  does  not 
take  place.  They  also  studied  experimentally  the  conditions 
of  house  infection,  and  their  work  is  among  the  best  planned 
and  executed  and  the  most  convincing  of  any  that  has  ever 
been  attempted  for  any  disease.  Besides  much  other  work, 
they  placed  guinea  pigs  in  the  houses  of  an  Indian  village 
just  vacated  by  the  inhabitants  because  of  plague,  thus  sub- 
stituting an  experimental  population  under  control  for  the 
normal  human  population.'  The  results  were  in  every  way 
in  accord  with  the  view  that  plague  is  primarily  a  rat  disease, 
and  is  transmitted  from  rats  to  man,  or  to  other  animals,  by 
means  of  fleas.  In  these  and  in  similar  less  extensive  experi- 
ments ^  there  was  evidence  to  show  that  the  animals  could 
not  contract  the  disease  from  the  dwellings  themselves.  To 
test  more  definitely  the  possibility  of  transmission  by  fomites 
other  experiments  were  made.  The  floors  of  houses  were 
soaked  with  cultures  of  the  bacilli,  and  guinea  pigs  placed 
upon  them.  Of  24  exposed  during  the  first  hour  after  in- 
fection 4  died;  of  12  exposed  up  to  six  hours  4  died;  but 
during  all  this  interval  pools  of  the  culture  were  upon  the 
floor.      Of   24  animals  exposed  after   twelve  hours  only   1 

'  Thompson,  J.  Hyfj;.,  CiiinhridKe,  1906,  VI,  537. 

'  Ham,  Rep.  on  PhiKuo  in  (Queensland,  1900-07,  Brisbane,  1907. 

'  J.  HyR.,  (\ambri(iKe,  1907,  VII,  799-875. 

*  J.  Ilyg.,  Cambridge,  1906,  VI,  450-482. 


INFECTION  BY  FOMITES  247 

succumbed.  Guinea  pigs  were  also  allowed  to  run  freely 
about  hospital  wards  in  which  cases  of  bubonic  plague  were 
being  treated,  and  15  w^ere  confined  in  a  room  with  freshly 
soiled  bedding,  which  was  renew^ed  every  day  for  six  weeks. 
In  none  of  the  animals  did  the  disease  develop.  Again  (p. 
887),  clothing  from  infected  houses,  removed  without  pre- 
cautions to  prevent  the  transport  of  fleas,  was  placed  in 
cages  containing  26  guinea  pigs,  1  of  which  died  of  the 
plague.  A  few  fleas  which  had  been  brought  in  the  clothing 
were  found  in  the  cages.  It  seems  to  be  quite  clear  from 
these  experiments  that  while  infection  by  fomites  is  pos- 
sible, it  is  probable  only  when  the  infection  is  exceedingly 
gross  and  the  contact  is  intimate,  as  in  the  case  of  the  in- 
fected floors  referred  to  above;  or  it  may  also  be  possible 
when  infected  fleas  are  transported  in  the  goods.  How 
common  this  is  has  not  yet  been  determined. 

Tuberculosis.  —  I  know  of  no  other  diseases  in  which  seri- 
ous experimental  work  has  been  done  to  determine  the  part 
played  by  fomites  in  their  diffusion.  It  is  particularly  re- 
markable that  tuberculosis  has  not  been  thus  critically 
studied.  Every  one  has  been  calling  for  room  disinfec- 
tion as  a  powerful  means  of  combating  this  disease,  yet  it 
does  not  seem  to  have  occurred  to  anyone  to  place  suscep- 
tible animals  in  a  series  of  supposedly  infected  rooms  (as 
was  done  in  the  case  of  plague  in  India)  to  determine  if  pos- 
sible how'  great  the  danger  from  room  infection  really  is. 

Disinfection  Unnecessary  after  Diphtheria.  —  By  a  study 
of  the  facts  presented  in  this  chapter  the  writer  was  con- 
vinced some  time  since  that  the  danger  from  fomites  in- 
fection is  for  most  diseases  very  much  less  than  is  generally 
believed.  In  diphtheria  particularly  it  appeared  that  little 
if  any  sickness  could  be  due  to  infection  remaining  about 
the  house  or  its  contents  after  the  termination  of  isolation. 
As  isolation  is  almost  invariably  terminated  without  any 
reference  to  the  presence  of  carriers  in  the  family,  it  ap- 
peared to  be  absurd  to  disinfect  the  material  things  in  the 


248       THE  SOURCES  AND   MODES  OF  INFECTION 

house  when  in  all  probability  some  carrier  was  still  growing 
the  bacilli.  Hence  in  March,  1905,  terminal  disinfection 
was  abandoned  in  Providence,  except  in  those  very  few 
instances  in  which  the  family  was  willing  to  wait  for  two 
successive  negative  throat  and  nose  cultures  from  each  of 
its  members.  The  attempt  was  thus  made  to  test  the  im- 
portance of  fomites  infection  by  abandoning  disinfection 
and  noting  any  change  that  might  occur  in  the  prevalence 
or  distribution  of  the  disease.  One  obvious  way  of  testing 
the  influence  of  disinfection  is  to  compare  the  recurrence  of 
the  disease  after  disinfection  with  the  amount  which  occurred 
after  the  warning  placard  was  removed  without  disinfection. 
The  following  shows  the  number  of  recurrences  within  60 
days  after  disinfection,  the  number  of  infected  families  and 
the  ratio  between  the  two,  during  the  years  1902  and  1905. 


Ye.\r. 

Infected 
Families. 

Recurrences. 

Ratio. 

1902 

1903 

1904 

1905 

358 
453 
559 

87 

1457 

6 

7 

10 
2 

25 

1.67 

1.54 
1.78 
2.30 

1.71 

Total 

The  following  shows  the  same  facts  where  there  was  no 
disinfection. 


Year. 

Infected. 
Families. 

Recurrences. 

Ratio. 

1905 

1900 

258 
259 
343 
G87 
472 
431 
550 

3000 

4 
4 

7 
17 
10 

4 

8 

54 

1.55 
1,55 
2.04 
2.34 
2.12 
.93 
1.49 

1.80 

1907 

1908 

1909 

1910 

1911 

Total 

INFECTION  BY  FOMITES 


249 


The  period  from  1902  only  is  taken,  because  previous  to 
that  time  the  duration  of  isolation  was  somewhat  longer,  but 
there  has  been  no  change  since.  Very  few  health  officers 
keep  any  record  of  the  recurrences  in  diphtheria  and  other 
infectious  diseases,  but  such  records  are  kept  in  Baltimore, 
where  terminal  disinfection  is  practiced  in  an  unusually 
thorough  manner,  and  is  in  a  large  majority  of  cases  tested 
for  its  efficiency.  In  order  to  make  the  Providence  figures 
comparable  to  those  of  Baltimore,  it  was  necessary  to  in- 
clude recurrences  in  other  families  in  the  house  as  well  as 
in  the  family  first  invaded,  and  to  calculate  the  percentage 
on  total  cases,  rather  than  on  invaded  households.  The 
following  are  the  figures  and  there  is  nothing  in  them  to 
indicate  that  terminal  disinfection  is  of  any  value  in  pre- 
venting recurrences. 


BALTIMORE.     DISINFECTION. 


Years. 

Cases. 

Recurrences. 

Ratio. 

1903-1909 

6931 

122 

1.76 

PROVIDENCE.     NO   DISINFECTION. 


Years. 

Cases. 

Recurrences. 

Ratio. 

1905-1911 

4189 

69 

1.64 

Again,  it  may  be  objected  that  recurrence  in  the  family  is 
no  criterion  of  the  infection  of  the  house,  for  it  may  be  that 
the  family  is  largely  immune.  This  would  certainly  be 
much  less  true  of  those  members  of  the  family  who  went 
away  during  the  sickness.  Of  634  minors  who  thus  re- 
turned to  the  non-disinfected  house  only  2  were  taken  sick. 
So,  too,  if  terminal  disinfection  is  such  an  important  matter. 


250       THE  SOURCES  AND  MODES  OF  INFECTION 

its  neglect  should  be  followed  by  an  increase  in  the  disease. 
As  a  matter  of  fact,  after  disinfection  was  abolished  diphthe- 
ria diminished,  until  at  one  time  in  the  following  August 
there  was  not  a  single  reported  case  in  the  city.  Again  in 
August,  1908,  the  disease  was  reduced  to  a  single  recog- 
nized case.  There  has  been  a  marked  increase  since,  common 
to  many  parts  of  New  England,  and  the  excess  in  Boston, 
where  disinfection  is  practiced,  has  been  greater  than 
in  Providence.  Still  another  test  of  the  danger  from  the 
omission  of  disinfection  is  the  extension  of  the  disease  to 
other  families  in  the  same  house.  Of  2592  such  families 
witli  susceptible  children  only  19  or  0.73  per  cent  were  in- 
vaded by  the  disease  within  two  months  after  the  termi- 
nation of  isolation  in  the  non-disinfected  apartment.  It 
may  be  suggested  that,  though  no  official  disinfection  was 
practiced,  the  houses  were  perhaps  thoroughly  cleansed  by 
the  occupants.  I  must  confess  that  I  hoped  that  the  aban- 
donment of  official  disinfection  would  cause  people  to  do 
more  cleansing  for  themselves,  but  there  has  thus  far  been 
little  improvement,  and  as  a  large  part  of  our  diphtheria 
occurs  among  poor  and  ignorant  people,  many  of  whom  are 
recent  immigrants,  house  cleaning  by  the  family  can  scarcely 
be  expected  to  be  very  efficient  at  present.  It  appears, 
then,  that  this  experiment  shows  that  house  infection  in 
diphtheria  is  in  Providence  a  negligible  factor  in  the  dis- 
semination of  the  disease. 

Disinfection  Unnecessary  after  Scarlet  Fever.  —  So  sim- 
ilar, from  an  epidemiological  standpoint,  are  scarlet  fever 
and  diphtheria  that  I  have  been  gradually  abandoning 
disinfection  after  the  former  disease  also.  The  following 
shows  the  recurrences  where  there  was  and  where  there  was 
not  official  disinfection. 

The  first  table  shows  the  number  of  recurrences  within 
GO  days  after  disinfection  for  scarlet  fever,  the  number  of 
infected  families,  and  the  rate  of  recurrence  during  the 
years  1904-09. 


INFECTION  BY   FO MITES 


251 


Year. 

Infected 
Families. 

Recurrences. 

Ratio. 

1904 

868 
298 
398 
540 
273 
52 

2429 

12 
2 
9 
8 
3 
3 

37 

1.38 

.67 
2.26 
1.48 
1.09 
5.77 

1.52 

1905 

1906 

1907 

1908 

1909 

Total 

During  the  last  four  years  the  recurrences  where  there 
was  no  disinfection  were  as  follows: 


Yeab. 

Infected 
Families. 

Recurrences. 

Ratio. 

1908 

1909 

1910 

1911 

Totals 

40 
377 
389 
434 

1240 

1 

10 

5 

4 

20 

2.50 

2.65 

1.29 

.92 

1.61 

As  in  diphtheria  so  in  scarlet  fever  the  infection  of  well 
persons  who  return  to  the  house  after  the  termination  of 
isolation  may  perhaps  be  a  measure  of  the  value  of  terminal 
disinfection.  In  Providence,  during  the  years  1887-89,  of 
1816  persons,  mostly  under  14  j-ears  of  age,  who  had  never 
had  scarlet  fever,  and  who  returned  home  after  disinfection, 
33,  or  1.8  per  cent,  developed  the  disease.  Of  207  persons 
who,  since  1908,  have  returned  to  non-disinfected  houses, 
3,  or  1.4  per  cent  have  contracted  scarlet  fever.  During 
the  years  1908-10,  of  138  persons  so  returning  none  were 
attacked.      The  only  apparent   recurrences  were  in  1911, 

Again  one  may  examine  the  recurrences  in  other  families  in 
the  same  house.  Of  1329  such  additional  families  in  1904- 
08  there  was  recurrence  within  two  months  after  disinfection 


252       THE  SOURCES  AND  MODES  OF  INFECTION 


in  21,  or  1.6  per  cent.  Of  1005  families  in  1909-11,  living 
in  houses  where  there  had  been  no  disinfection,  there  were 
recurrences  in  15,  or  1.5  per  cent. 

A  further  comparison  showing  the  results  with  and  with- 
out disinfection  can  be  made  with  the  data  from  Baltimore. 
To  make  these  comparable  to  the  Providence  figures  there 
have  been  included,  in  the  latter,  recurrences  in  other  fam- 
ilies in  the  same  dwelling.  The  ratio  is  calculated  on  the 
number  of  cases  instead  of  on  the  number  of  families  as  in 
the  table  next  preceding. 


Baltimore. 

Disinfection. 

Years. 

Cases. 

Recurrences. 

Ratio. 

1903-09 

5792 

84 

1.44 

Providence.    No 

Disinfection. 

Years. 

Cases. 

Recurrences. 

Ratio. 

1908-11 

1801 

31 

1.72 

The  health  commissioner  of  Buffalo  ^  reports,  as  illustrat- 
ing the  efficacy  of  disinfection,  that  after  3029  cases  of 
scarlet  fever  where  terminal  disinfection  was  practiced  and 
tested,  there  were  117  recurrences,  or  3.8  per  cent. 

Disinfection  Unnecessary  in  Other  Diseases.  —  In  any 
disease  which  is  widely  distributed,  and  in  which  there  is 
ample  opportunity  for  extension  from  mild  cases,  from  car- 
riers, from  cases  in  the  early  stages,  and  from  convalescents, 
the  absolute  disinfection  of  all  possible  fomites  at  the  as- 
sumed termination  of  the  sickness  will  probably  have  no 
influence  in  checking  the  disease.  Thus  I  can  see  no  use  in 
disinf(!cting  after  measles,  whooping  cough,  influenza,  pneu- 
monia or  c{'rehro-si)inal  meningitis,  and  1  think  that  this 
1  Ecp.  Dcpt.  of  Health.  1909,  20,  44. 


INFECTION  BY  FOMITES  253 

view  is  held  by  the  majority  of  our  health  officers  and  epi- 
demiologists. In  fact  it  is  the  expressed  opinion  of  most 
health  officers  that  disinfection  after  measles  is  unneces- 
sary, as  there  is  no  evidence  that  fomites  are  a  factor  in  the 
spread  of  the  disease.  Disinfection  after  measles,  which 
was  practiced  in  Aberdeen  for  twenty  years,  had  no  influ- 
ence on  the  prevalence  of  the  disease.  When  official  dis- 
infection after  measles  was  temporarily  suspended  in  New 
York  from  January  10,  1908,  to  March  1,  neither  the  sus- 
pension nor  the  resumption  of  the  practice  appeared  to 
have  any  effect  on  the  epidemic  curve.  Disinfection  after 
cerebro-spinal  meningitis  is  also  absurd,  as  the  meningo- 
coccus lives  only  a  few  hours,  and  carriers  are  almost  the 
sole  means  by  which  this  disease  is  spread.  This  is  coming 
to  be  the  accepted  view  and  in  a  recent  publication  of  the 
U.  S.  Public  Health  Service  ^  Frost  makes  no  mention  of 
terminal  disinfection  among  prophylactic  measures.  Much 
disinfection  after  tuberculosis  is  also  without  reason.  If  a 
patient  has  been  living  with  his  family  and  taking  no  pre- 
cautions, certainly  no  amount  of  terminal  disinfection  will 
atone  for  long-continued  sanitary  sin.  If  precautions  are 
taken,  the  phthisiologists  tell  us  that  there  is  no  danger  in 
living  with  the  patient,  and  if  so,  certainly  there  can  be  no 
possible  danger  in  living  in  his  house  after  he  is  dead. 
The  only  occasion  for  disinfection  after  consumption,  then, 
is  when  the  apartments  of  a  careless  patient  are  to  be  occu- 
pied by  another  family,  and,  after  all,  we  have  no  evidence 
to  show  how  much  danger  there  is  even  then.  Yet  many 
health  officers  make  disinfection  after  every  death  from 
consumption  the  first  and  often  the  only  measure  taken  to 
restrict  tuberculosis. 

Dr.  William  C.  Woodward  of  Washington  in  the  discus- 
sion of  a  paper  read  before  the  American  Public  Health 
Association  presented  some  figures  which  he  believes  indi- 

1  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Pub.  Health  Rep.,  1912, 
XXVII,  97. 


254       THE  SOURCES  AND  MODES  OF  INFECTION 

cate  that  terminal  disinfection  after  tuberculosis  is  a  valu- 
able prophylactic  measure.  He  says  that  during  a  period 
of  about  two  years  ending  in  May,  1910,  1650  houses  in 
Washington  were  disinfected  because  of  tuberculosis.  Sub- 
sequent to  the  disinfection  there  were  reported  from  the 
disinfected  houses  cases  of  tuberculosis  sufficient  to  give 
an  annual  attack  rate  of  223  while  the  attack  rate  through- 
out the  remainder  of  the  population  was  414. 

Even  in  smallpox  there  are  bits  of  evidence  to  show  that 
fomites  play  an  unimportant  part.  Jordan  ^  refers  to  two 
unvaccinated  men  who  fumigated  and  handled  infected 
smallpox  clothing  for  two  months  without  contracting  the 
disease  but  who  succumbed  to  it  as  soon  as  they  came  in 
contact  with  patients. 

School  Disinfection.  —  When  a  number  of  cases  of  scar- 
let fever  or  diphtheria  develop  in  a  school,  the  public  is  in- 
clined to  consider  room  infection  the  source  and  to  demand 
"  disinfection."  This  subject  has  lately,  perhaps  owing  in 
part  to  the  efforts  of  sellers  of  disinfectants,  been  much  dis- 
cussed in  England,  but  fortunately  the  leading  officials 
refuse  to  be  influenced  by  public  clamor.  Among  others, 
Kerr  ^  has  clearly  set  forth  the  reasons  why  the  room  can 
rarely  be  at  fault  in  school  outbreaks  of  the  contagious 
diseases.  In  another  place  Kerr  ^  reports  26  instances  in 
which  scarlet  fever  patients  in  the  desquamating  stage  were 
found  in  school.  In  2  instances  the  room  was  disinfected 
after  their  removal  and  in  1  of  these  a  secondary  case  de- 
veloped 9  days  later.  In  the  other  24  instances  there  were  2 
secondary  cases.  Hope''  says,  "All  evidence  points  strongly 
to  the  fact  that  when  children  contract  infectious  disease  in 
school  the  channel  of  infection  is  not  by  means  of  school 
desk  or  floor  but  by  the  personal  infection  of  another  child." 

1  Jonhui,  Am.  J.  Tul).  Ilytr.,  1910,  YI,  7.^)5. 

2  Kerr,  Pub.  Iloallh,  Lond.,  1909,  XXIII,  49. 

'  Kerr,  Rop.  M(h1.  Off.  Education,  Lond.,  1909,  59. 

*  Hope,  llcp.  to  Education  Authority,  Liverpool,  1909,  9. 


INFECTION  BY  FOMITES  255 

French  Views  on  Disinfection.  —  Recently/  at  a  discus- 
sion in  Paris,  Comby,  Courmont  and  Lemoine  took  the 
ground  that  the  active  disinfection  which  has  been  insisted 
on  in  that  city  in  recent  years  has  not  reduced  the  mortaUty 
from  scarlet  fever,  diphtheria  or  measles,  for  which  dis- 
eases it  is  required.  Comby  ^  is  emphatic  in  his  contention 
that  it  is  persons,  not  things,  that  are  the  bearers  of  con- 
tagion. The  same  position  was  taken  by  Semaine  medicale 
for  February  14,  1906.  Lemoine  ^  has  found  disinfection 
not  so  essential  as  has  been  claimed.  At  the  hospital  at 
Val  de  Grace  certain  rooms  were  used  for  isolating  single 
cases  of  contagious  disease.  There  was  often  such  demand 
for  their  use  that  cases  of  different  diseases  quickly  suc- 
ceeded one  another,  sometimes  without  any  disinfection 
and  often  with  slight  disinfection  by  washing  the  walls  as 
high  as  could  be  reached.  Sixty-five  cases  of  scarlet  fever, 
41  of  measles,  25  of  mumps,  31  of  diphtheria,  4  of  smallpox, 
1  of  chicken  pox  and  136  of  other  diseases  are  reported  as 
rapidly  succeeding  one  another  in  these  rooms.  One  case 
of  measles  and  4  of  scarlet  fever  developed  in  the  rooms. 
Often  it  was  necessary  to  shift  entire  wards  of  twenty  to 
thirty  beds,  with  only  a  slight  attempt  at  disinfection. 
This  was  done  a  good  many  times  during  nine  years  with- 
out bad  results.  We  have  had  a  similar  experience  at  the 
Providence  City  Hospital  where  no  attempt  is  made  to 
disinfect  the  walls  and  ceilings  of  the  cubicles  in  which 
different  diseases  rapidly  succeed  one  another,  and  there 
has  never  been  an  instance  in  which  infection  could  pos- 
sibly be  attributed  to  neglect  of  this  rite. 

English  Views.  —  There  is  a  growing  tendency  on  the 
part  of  many  English  health  officials  to  attach  less  impor- 
tance to  the  part  played  by  fomites  in  the  spread  of  disease 
and   consequently  less  value  to   terminal   disinfection  as 

1  Bull,  et  m6m.  Soc.  med.  d.  hop.  de  Par.,  1909,  n.  s.,  XXVII,  585. 

2  Comby,  Presse  med.,  Paris,  1909,  XXVII,  249. 

3  Lemoine,  Rev.  d'hyg.,  1907,  XXIX,  1057. 


256       THE  SOURCES  AND  MODES  OF  INFECTION 

ordinarily  practiced.  Richards  ^  does  not  consider  disin- 
fection of  the  room  necessary,  provided  the  floors  are 
washed  and  things  which  came  in  contact  with  the  patient 
are  cleansed  and  disinfected.  Butler,  Barlow,  Hogarth 
and  others  have  expressed  a  growing  belief  that  fomites 
play  a  comparatively  unimportant  part  in  the  spread  of 
disease.  The  views  of  Hope  and  Kerr  are  referred  to 
above.  The  writer  has  received  a  number  of  letters  from 
English  and  Colonial  medical  officers  of  health  indicating 
agreement  with  the  main  proposition  of  this  chapter. 

American  Views.  —  It  is  not,  of  course,  to  be  expected 
that  the  majority  of  health  officers  would  be  willing  to 
abandon  terminal  disinfection  as  now  practiced.  There  are, 
however,  very  many  of  the  most  thoughtful,  and  at  the 
same  time  most  conservative,  who  agree  that  the  present 
methods  of  disinfection  should  either  be  made  really  effi- 
cient or  else  given  up.  They  are  ready  to  admit  that 
fomites  are  a  far  less  important  factor  in  the  spread  of  dis- 
ease than  was  formerly  thought,  but  they  think  that  even 
minor  factors  should  if  possible  be  efficiently  controlled. 
A  few  health  officers  are  willing  to  test  the  matter  for 
themselves  and  have  given  up  or  are  gradually  omitting 
gaseous  disinfection  after  scarlet  fever  and  especially  after 
diphtheria.  The  health  officer  of  one  important  American 
city  was  trying  gradually  to  abandon  terminal  disinfection 
until  his  progressive  attitude  was  frowned  upon  by  the 
state  health  officials.  In  Newton  disinfection  is  not  com- 
pulsory. 

When  Terminal  Disinfection  is  Desirable.  —  When  a  new 
or  rare  disease  invades  a  locality,  it  may  at  times  be  desir- 
able to  take  extraordinary  precautions  to  j^revent  its  exten- 
sion, whicli  would  be  entirely  useless  if  the  disease  were 
established.  This,  it  is  true,  is  not  the  popular  or  legal  way 
of  regarding  preventive^  measures,  but  it  is  the  scientific 
one.  If  a  case  of  smallpox  should  occur  in  Providence, 
»  Richards,  Pul).  Health,  LoiuL,  1909,  XXIII,  42. 


INFECTION  BY  FOMITES  267 

which  has  been  free  from  it  for  several  years,  it  would  be 
worth  while,  perhaps,  to  expend  considerable  time  and 
money  in  disinfection,  even  though  the  chance  of  infection 
from  the  rpom  or  goods  might  not  be  one  in  a  thousand. 
But  if  there  were  hundreds  of  cases  of  measles  in  the  city, 
it  would  be  folly  to  go  to  the  same  trouble  and  expense  for 
each  case,  even  if  the  chance  of  infection  were  ten  times  as 
great.  A  spark  in  the  dry  grass  should  be  stamped  out  at 
any  cost,  but  it  is  useless  to  waste  time  in  extinguishing  the 
smoldering  flames  left  here  and  there  as  the  line  of  fire  is 
sweeping  across  the  prairie. 

Objections  to  Disinfection.  —  There  are  several  objec- 
tions to  the  present  practice  of  terminal  disinfection.  One 
is  that  it  only  partially  disinfects.  If  disinfection  is  to  be 
honestly  and  efficiently  applied,  methods  must  be  changed. 
But  even  as  now  practiced,  disinfection  is  expensive.  Many 
cities  employ  disinfectors,  with  horses  and  apparatus,  while 
their  laboratory  languishes,  their  medical  inspection  is  poor 
and  their  diphtheria  patients  must  secure  antitoxin  as  best 
they  can.  Another  serious  objection  to  routine  terminal 
disinfection  is  that  it  misleads  the  public.  They  are  given 
a  false  sense  of  security,  and  they  are  encouraged  in  the  old 
belief  that  it  is  things,  not  persons,  which  are  dangerous. 
We  can  never  successfully  preach  the  truth  about  carriers, 
or  teach  the  necessity  for  stricter  personal  cleanliness,  so 
long  as  we  continue  to  make  so  much  of  a  fetish  of  the 
practice  of  disinfection. 

Cleanliness  versus  Disinfection.  —  I  am  here  referring  to 
terminal  disinfection,  which  is  often  only  a  fumigation,  or 
smell-producing  process.  The  continued  practice  of  clean- 
liness all  through  the  sickness,  and  indeed  at  all  times,  by 
which  the  transference  of  fresh  infective  material  may  be 
prevented,  is  another  matter,  the  value  of  which  was  con- 
sidered in  the  preceding  chapter. 

Conclusions.  —  It  seems  to  me,  in  view  of  the  considera- 
tions here  presented,  that  we  are  justified  in  concluding  that, 


258       THE  SOURCES  AND  MODES  OF  INFECTION 

1.  There  is  no  good  epidemiological  evidence  that  any 
diseases  except  those  due  to  spore-forming  bacteria  are  to 
any  great  extent  transmitted  by  fomites. 

2.  Judging  from  our  experience  with  yellow  fever  most  of  the 
alleged  evidence  of  infection  by  fomites  is  not  to  be  relied  upon. 

3.  Even  if  all  the  alleged  fomites  infection  is  real,  only  a 
very  small  part  of  contagious  disease  is  traceable  to  this 
source. 

4.  The  theory  of  fomites  infection  was  an  a  priori  not  an 
a  posteriori  theory,  and  is  no  longer  demanded. 

5.  Other  modes  of  transmission  so  much  more  satisfac- 
torily account  for  the  spread  of  disease,  that  there  seems 
to  be  really  little  opportunity  for  infection  by  fomites. 

6.  Laboratory  investigation  shows  that  fomites  infection 
with  spore-forming  bacteria  is  common;  that  such  infection 
in  typhoid  fever,  tuberculosis,  diphtheria  and  with  other 
resistant  organisms  doubtless  sometimes  takes  place;  that 
it  is  possible  in  cholera  and  plague,  while  such  infection  in 
gonorrhea,  influenza,  cerebro-spinal  meningitis  and  pneu- 
monia must  be  practically  impossible. 

7.  Experiment  and  epidemiological  observation  have 
demonstrated  that  fomites  infection  is  practically  unknown 
in  yellow  fever  and  is  probably  so  in  the  other  diseases  car- 
ried by  flying  insects. 

8.  Experiment  and  observation  show  that  fomites  are  of 
little  moment  in  the  diffusion  of  bubonic  plague,  and  of  no 
moment  in  the  extension  of  Mediterranean  fever,  both 
formerly  believed  to  be  spread  in  this  way. 

9.  Observations  made  in  Providence  indicate  that  fo- 
mites  infection  is  of  no  practical  importance  in  the  diffusion 
of  diphtheria. 

10.  Observations  in  Providence  indicate  that  fomites  are 
of  no  practical  importance  in  the  diffusion  of  scarlet  fever. 

Finally,  it  may  be  affirmed  that  the  evidence  has  been 
r:ii)i(lly  accumulaiiug  that  f()mit(>s  infection  is  of  very  much 
less  importance  than  was  formerly  believed. 


CHAPTER  VI. 

INFECTION    BY   AIR. 

Reasons  for  Former  Belief.  —  From  time  immemorial  the 
air  has  been  considered  the  chief  vehicle  of  infection.  This 
was  but  natural,  for  until  recently  the  virus  of  the  infectious 
diseases  was  believed  to  be  gaseous,  or  at  least  readily  dif- 
fusible, and  readily  borne  by  air  currents.  The  infective 
material  was  supposed  to  be  given  off  in  the  expired  breath, 
and  to  emanate  from  the  surface  of  the  body  and  from  moist 
soil  and  decomposing  matter  of  all  kinds.  Contagious  dis- 
eases were  known  to  arise  without  any  apparent  connection 
with  other  cases,  and  what  could  be  more  natural  than  to 
assume  that  the  invisible,  imponderable  materies  morbi  is 
mixed  with  and  carried  by  the  air?  Moreover  one  of  the 
most  widespread  and  best  known  diseases,  malaria,  was 
shown  by  a  great  mass  of  clinical  evidence  to  be  an  air-borne 
disease,  and  yellow  fever,  another  infectious  disease  of  great 
importance,  was  also  on  good  grounds  believed  to  be  trans- 
mitted in  the  same  manner.  What  seemed  to  be  well  estab- 
lished for  these  two  diseases  was  assumed  on  much  more 
slender  evidence  to  be  true  of  most,  if  not  all,  the  infectious 
diseases.  It  is  true  in  a  certain  sense  that  the  two  diseases 
just  mentioned  are  air-borne,  that  is,  they  are  transmitted  by 
small  insects,  which  "  diffuse,"  as  it  were,  from  their  breeding 
places  vand  are  readily  wafted  by  air  currents.  It  is  not  in 
this  sense  that  the  term  air-borne  is  used  in  this  chapter,  but 
the  inquiry  here  made  is  whether  the  virus  of  the  infectious 
diseases  is  borne  by  the  air,  either  free  or  attached  to  small 
particles  of  inanimate  matter. 

Then,  again,  the  first  symptoms  of  measles,  and  often  of 
influenza,  are  connected  with  the  nose,  diphtheria  appears  to 
be  a  throat  disease,  while  consumption  and  pneumonia  infect 

259 


260       THE  SOURCES  AND  MODES  OF  INFECTION 

the  lungs.  What  is  more  natural  than  to  assume  that  the  air 
which  bathes  these  parts  is  the  vehicle  of  infection  ?  But  since 
it  has  been  shown  that  the  pneumococcus  is  constantly  found 
in  the  blood  in  pneumonia,  and  has  been  demonstrated  before 
the  initial  chill,  and  since  tubercle  bacilli  readily  reach  the  lungs 
through  the  circulation,  the  force  of  this  argument  is  lost. 

Omitting  the  insect-borne  diseases,  let  us  see  first  what 
epidemiological  evidence  there  is  that  the  contagious  diseases 
are  air-borne. 

Smallpox  Air-borne  from  Hospitals.  —  Smallpox  is  be- 
lieved to  be  more  widely  air-borne  than  is  any  other  disease. 
The  modern  doctrine  of  the  aerial  transmission  of  smallpox 
received  its  greatest  support  from  the  investigations  of  Power  ^ 
in  1881  concerning  the  conditions  about  the  Fulham  Hospital 
in  London.  That  smallpox  could  be  carried  by  the  air  long 
distances  had  been  claimed  by  many  before  that  time,  for 
Dr.  Waterhouse  of  Cambridge,  more  than  one  hundred  years 
ago,  believed  the  disease  had  been  wafted  across  from  Boston 
to  Charlestown,  though  later  he  was  inclined  to  deny  this 
mode  of  transmission.  Power  showed  that  smallpox  had  not 
prevailed  to  any  extent  in  the  vicinity  of  the  Fulham  Hospital 
before  the  hospital  was  opened,  and  that  on  a  number  of  occa- 
sions soon  after  it  was  occupied  by  a  considerable  number  of 
patients  the  disease  began  to  develop  in  the  neighborhood. 
Furthermore  he  showed  that  there  was  a  progressive  decrease 
in  the  amount  of  smallpox  as  the  distance  from  the  hospital 
increased,  the  alleged  influence  of  the  hospital  extending  to 
at  least  one  mile.  It  was  furthermore  shown  by  the  doctor 
that  this  distribution  of  the  disease  was  uniform  in  every 
direction  from  the  hospital,  that  is,  in  every  quadrant  of  the 
circle  surrounding  it.  Later  investigations  at  this  hospital 
yielded  similar  data.^  Smallpox  almost  always  developed 
in  the  vicinity  whenever  the  hospital  was  occupied  by  from 

1  Rep.  Med.  OfT.  Loc.  Gov.  Bd.,  Lond.,  1880-81,  X,  Supl.  302. 
'  Hep.  Med.  OfT.  Loc.  Gov.  Bd.,  Lend.,  1884-85,  XIV,  55,  1885-86, 
XV,  111. 


INFECTION  BY  AIR  261 

eighty  to  one  hundred  acute  cases.  But  on  one  occasion,  at 
least,  there  was  no  outbreak  even  when  the  hospital  was  fully 
occupied.  The  conclusion  was  that  when  a  considerable 
number,  eighty  to  one  hundred,  acute  cases  of  smallpox  are 
gathered  in  a  hospital,  there  is  great  danger  that  the  virus 
of  the  disease  will  be  carried  by  the  air  a  mile  or  more  from 
the  hospital  in  quantity  sufficient  to  infect  persons  at  that 
distance.  Powers  considered  that  the  hospital  was  thus  the 
focus  of  infection  on  one  occasion  when  there  were  only 
twenty  patients,  and  at  another  time  when  there  were  only 
nine,  of  which  five  were  acute.  It  was  thought,  from  a  study 
of  the  conditions  at  the  time  of  the  outbreak,  that  the  dis- 
semination was  favored  by  still,  damp  weather.  A  somewhat 
similar  though  not  generally  so  well  defined  or  nicely  graded 
distribution  of  smallpox  around  hospitals  was  believed  by 
many  to  have  been  demonstrated  in  the  cases  of  the  Homerton, 
Deptford,  and  Hempstead  hospitals.  It  was  natural  that 
twenty-five  years  ago,  when  knowledge  of  modes  of  infection 
was  far  more  vague  than  at  the  present  time,  and  with  such 
evidence  at  hand,  the  officers  of  the  Local  Government  Board 
should  have  been  firmly  convinced  of  the  importance  of  aerial 
transmission  in  the  spread  of  smallpox,  and  that  this  opinion 
should  have  been  shared  by  many  medical  officers  of  health. 
Subsequent  to  the  investigations  referred  to  above,  outbreaks 
due  to  the  spread  of  this  disease  from  hospitals  are  said  to 
have  occurred,  among  other  places,  at  West  Ham,  1884-85,^ 
Nottingham,  1887-88,'  Oldham,  1888  and  1892,'  Warrington, 
1892-93,"  Bradford,  1893,'  Liverpool,  1902-03,"  and  in  Gates- 

1  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  Lond.,  1886-87,  XVI,  97. 

^  Whitelegge,  Practitioner,  Lond.,  1888,  XLI,  65. 

'  Report  on  the  Health  of  Oldham,  1892,  by  Niven;  also  Niven,  Pub. 
Health,  1892-93,  V,  324,  366. 

*  Gomall,  Rep.  on  the  Epidemic  of  Smallpox  in  the  years  1892-93 
In  Warrington,  188.5,  111. 

"  Evans,  Brit.  M.  J.,  Lond.,  1894,  II,  356. 

«  Reece,  Special  Rep.  Loc.  Gov.  Bd.,  Lond.,  No.  208.  1905,  Smallpox 
in  Liverpool. 


262        THE  SOURCES  AND  MODES  OF  INFECTION 

head  and  Felling,  1903-04.^  In  Glasgow-  Chalmers  states 
that  smallpox  seemed  to  develop  around  the  hospital  when 
it  contained  many  patients,  but  that  this  did  not  invariably 
occur.  When  the  hospital  was  removed  to  another  location, 
it  again  appeared  to  be  a  focus  of  disease.  Much  has  been 
made  of  the  alleged  aerial  transmission  of  smallpox  from  the 
ships  lying  in  the  Thames  below  London  and  used  for  the 
reception  of  cases  of  that  disease  from  the  metropolis.  Bu- 
chanan^ and  Thresh*  attempt  to  show  that  after  the  ships 
were  brought  into  use  the  disease  was  carried  by  the  air  to 
the  Essex  shore  at  Purfleet  and  West  Thurrocks  in  the  Orsett 
Union.  It  is  true  enough  that  the  incidence  of  the  disease 
was  very  great  in  these  districts,  but  it  is  difficult  to  under- 
stand why  it  is  not  as  well  explained  by  contact  infection,  as 
were  hundreds  of  similar  outbreaks  in  England  and  the  United 
States.  The  chief  evidence  on  which  the  theory  of  aerial 
infection  is  based  is  the  existence  around  the  hospital,  in 
every  quadrant,  of  a  graduated  incidence  of  the  disease.  No 
such  evidence  is  presented  in  this  instance,  and  the  area  of 
infection  attributed  to  the  ships  lies  only  in  one  direction 
from  them.  Smallpox  appeared  on  the  shore  nearest  the 
ships,  and  then  gradually  extended  to  a  distance  of  two  or 
three  miles.  This  sort  of  extension  is  just  what  would  be 
expected  in  contact  outbreaks.  If  air-borne,  the  near  and 
distant  communities  should  have  been  affected  at  the  same 
time.  It  was  claimed  by  Dr.  Thresh  that  the  influence  of 
the  ships  could  be  noted  at  a  distance  of  four  or  five  miles. 
It  was  also  claimed  that  several  vessels  anchored  near  the 
hospital  ships developed  smallpox  twelve  days  later.  That 
ships  leaving  London  during  the  period  of  the  extensive  out- 

^  Buchanan,  Special  Rep.  Loc.  Cov.  Bd.,  Lond.,  Smallpox  in  Gates- 
head and  FellinR,  1904. 

»  J.  Royal  San.  Inst.,  1905,  XXVI,  212,  and  Tr.  Epidemiol.  See, 
Lond.,  1904-05,  n.  s.,  XXIV,  151,  244. 

'  Rep.  Mod.  Off.  Loc.  (\ov.  Bd.,  Lond.,  1902-0:^,  XXXIl,  81. 

«  Thresh,  Tr.  Epidemiol.  Soc,  Lond.,  1902,  n.  s.,  XXI,  101. 


INFECTION  BY  AIR  263 

break  in  that  city  should  occasionally  carry  smallpox  with  them 
is  not  remarkable.  Finally  it  was  admitted  that  surrepti- 
tious communication  with  the  ships  occasionally  occurred. 

Aerial  Convection  Denied  by  Some.  —  Many  sanitary  offi- 
cials did  not,  and  do  not,  accept  these  conclusions,  and  nu- 
merous instances  are  given  where  the  disease  has  not  extended 
from  hospitals.  Thus  Renney-  says  that  in  1883-84  he  saw 
300  cases  of  smallpox  treated  in  wards  which  were  situated 
between  twenty  and  two  hundred  and  twenty-four  feet  of 
other  hospital  wards,  schools  and  houses,  without  any  exten- 
sion, though  only  the  school  was  protected  by  vaccination. 
At  another  time  he  saw  a  considerable  number  of  cases  cared 
for  without  harm  in  a  ward  from  forty  to  one  hundred  and 
thirty-eight  feet  from  other  occupied  buildings.  So  Wilson  at 
Rugby^  had  a  hospital  within  a  few  yards  of  a  much  fre- 
quented road  with  no  untoward  results.  At  many  other 
times  he  has  seen  smallpox  hospitals  maintained  in  close 
proximity  to  other  occupied  buildings  without  aerial  trans- 
mission resulting.  Boobbyer^  treated  20  cases  near  a  high- 
way where  a  thousand  workmen  passed  daily,  and  not  a  case 
was  contracted  from  them.  Ker^  at  Edinburgh  had  a  small- 
pox hospital  in  connection  with  a  general  hospital,  and  close  to 
other  institutions,  and  with  a  population  of  3000  persons  liv- 
ing within  a  mile  circle.  There  were  only  4  cases  within  this 
circle,  of  which  2  were  known  to  be  contracted  elsewhere. 
Dr.  Thome  Thorne^  stated  that  in  two  instances  only  had 
he  seen  evidence  of  the  aerial  extension  of  smallpox  from  a 
hospital,  namely,  at  Maidstone  and  at  Stockton,  while  he  had 
seen  numerous  instances  where  there  was  no  extension, 
notably  at  Leeds  and  Nottingham. 

1  Renney,  Jour.  Roy.  San.  Inst.,  1905,  XXVI,  210. 
«  Wilson,  Brit.  M.  J.,  Lond.,  1905,  II,  630. 

3  Boobbyer,  Tr.  Epidemiol.  Soc,  Lond.,  1905,  n.  s.,  XXIV,  219. 
*  Ker,  Tr.  Epidemiol.  Soc,  Lond.,  1905,  n.  s.,  XXIV,  174. 
5  Thorne  Thome,  Rep  Med.  Off.  Loc.  Gov.  Bd.,  Lend.,  1880-81, 
X,  Supl.  40. 


264        THE  SOURCES  AND  MODES  OF  INFECTION 

At  Manchester  Niven^  reported  only  13  smallpox  cases 
out  of  a  population  of  over  40,000  living  within  a  half  mile 
to  a  mile  area  around  the  hospital  and  none  among  the  606 
persons  living  within  the  half-mile  circle.  Other  instances 
can  be  given  where  smallpox  hospitals  have  not  infected 
their  neighborhood,  and  these  facts  should  have  some  weight, 
though  according  to  the  advocates  of  the  theory  aerial  trans- 
mission is  to  be  expected  only  under  certain  conditions  of 
the  atmosphere.  There  is  not  much  evidence  bearing  upon 
this  subject  to  be  obtained  in  the  United  States,  partly 
because  smallpox  hospitals  have  been  much  more  rarely 
situated  in  thickly  populated  districts  and  partly  because 
less  attention  has  been  given  to  the  subject  here  than  in 
England. 

American  Evidence  against  Theory.  —  In  Philadelphia  it 
is  claimed "  that  the  hospital  has  been  the  source  of  smallpox 
in  its  neighborhood.  Thus  in  one  outbreak  in  the  municipal 
ward  in  which  the  hospital  was  situated  the  case  rate  was 
61  per  10,000,  nearly  twice  that  of  any  other  ward,  and  it 
decreased  as  the  distances  from  the  hospital  increased.  The 
same  conditions  were  noted  in  another  outbreak. 

In  Boston  in  1902-03  there  was  some  discussion  as  to 
whether  the  disease  spread  from  the  hospital,  which  was 
on  a  busy  street  and  near  many  occupied  buildings.  The 
evidence  was  that  there  was  not  nmch  smallpox  in  the 
neighborhood,  and  also  that  contact  infection  from  the  hos- 
pital could  not  be  excluded. 

In  New  Orleans^  a  large  number  of  cases  of  smallpox  were 
in  1900  treated  in  a  hospital  in  close  proximity  to  a  dense 
population,  but  without  evidence  of  ext(nisi()n.  Dr.  Th^ard 
writes  me  that  his  observations,  extending  over  nine  years 
since  that  time,  have  only  strengthened  his  views  then  ex- 
pressed, namely,  that  smallpox  virus  is  not  carried  from  hos- 

'  Nivon,  Tr.  Epiflciniol.  Soc,  Lond.,  1005,  n.  s.,  XXIV,  157. 

»  Rvp.  Hii.  of  lIojiKli,  Phihi.,  1903,  29. 

'  Rep.  IJd.  Health  of  tlie  City  of  New  Orleans,  1900-01,  33. 


INFECTION  BY  AIR  265 

pitals  by  the  air.  In  Brooklyn  smallpox  is  cared  for  at  the 
contagious-disease  hospital,  in  pavilions  about  twenty  feet 
from  those  occupied  by  measles  and  scarlet-fever  patients. 
There  has  been  no  extension  of  the  disease,  though  this  may 
be  largely  due  to  the  effort  to  keep  the  other  patients  well 
protected  by  vaccination.  But  there  is  also  a  considerable 
population  within  a  mile  of  the  hospital  which  has  never  been 
injuriously  affected  by  it.  In  Providence  the  smallpox  hos- 
pital is  distant  only  four  hundred  or  five  hundred  feet  from  a 
number  of  cottages  and  an  excursion  ground  frequented  by 
hundreds  of  persons  daily.  It  is  true  that  only  about  a  dozen 
patients  have  ever  been  there  at  one  time,  but  it  is  hard  to 
understand  vfhy  ten  patients  should  not  be  more  dangerous 
at  five  hundred  feet  than  one  hundred  patients  a  mile  dis- 
tant. In  Detroit,  Dr.  Kiefer  writes  me,  there  has  been  no 
extension  from  the  hospital,  and  in  Chicago  ^  there  was  less 
smallpox  around  the  hospital  than  in  other  parts  of  the  city. 
Theoretical  Objections.  —  I  have  been  led  to  question 
this  theory  of  the  aerial  transmission  of  smallpox  for  various 
reasons.  From  what  is  known  of  the  nature  of  the  virus  of 
so  many  other  diseases  it  seems  highly  improbable  that  they 
are  carried  any  great  distance  by  the  air,  and  in  fact  it  is 
only  for  smallpox  that  this  mode  of  transmission  is  claimed. 
But  smallpox  virus  is  certainly  solid  matter,  and  it  certainly 
after  a  time  loses  its  vitality,  and  in  all  respects  other  than 
the  one  under  consideration  it  behaves  not  unlike  the  mate- 
ries  morhi  that  we  are  better  acquainted  with.  Again,  it 
would  be  most  remarkable,  if  the  disease  extends  from,  say, 
one  hundred  cases  to  the  distance  of  a  mile  with  sufficient 
intensity  to  infect  many  persons,  that  it  should  not  extend 
one  hundred  feet  from  ten  cases  or  even  from  one  case.  Why 
should  we  not  expect  aerial  infection  frequently  to  operate 
at  short  distances  from  single  cases  ?  Yet  such  transmission 
does  not  occur  unless  it  be  with  great  rarit3\  How  rare  it  is 
for  any  claim  to  be  made  that  this  disease  has  been  carried 
1  Rep.  Health  Dept.,  Chicago,  1907-10,  60.' 


266         THE  SOURCES  AND  MODES  OF  INFECTION 

across  the  street  from  house  to  house,  and  how  unique  a  rigid 
demonstration  of  such  an  occurrence  would  be!  How  often 
a  single  case  in  a  crowded  lodging  house,  ship's  steerage,  or 
hospital  ward,  fails  to  infect  others!  Yet  we  are  asked  to 
believe  that  one  hundred  cases  can  give  rise  to  a  whole  circle 
of  cases  a  half  mile  away.  Either  the  amount  of  virus  must 
depend  upon  the  number  of  patients,  or  it  must  under  hospi- 
tal conditions  develop  in  some  marvelous  way  outside  of 
the  body. 

Contradictions  in  Claims.  —  If  the  evidence  adduced  in 
favor  of  this  theory  is  examined,  several  suspicious  circum- 
stances are  noticed.  It  is  very  curious  that  a  material  sub- 
stance should  be  borne  by  the  air  without  reference  to  air 
currents ;  yet  in  the  earlier  reports  by  Powers  all  evidence  of 
such  currents  was  lacking.  It  is  true  that  in  later  reports 
the  wind  has  been  claimed  as  a  factor,  as  at  Gateshead  and 
Felling,  but  the  evidence  in  this  case  has  been  made  valueless 
by  more  detailed  search  for  the  origin  of  the  cases.  At  Liver- 
pool the  disease  was  distributed  in  different  directions  around 
the  three  hospitals,  so  that  if  air-borne  it  must  have  been 
independent  of  air  currents.  Savill  at  Warrington  even 
claimed  that  the  virus  diffused  against  the  wind.  The  reports 
of  the  Fulham  Hospital  give  one  the  impression  that  the 
virus  of  smallpox  must  diffuse  like  a  gas,  which  certainly  is  not 
thinkable.  If  air-borne  at  all,  it  must  be  carried  as  is  dust  or 
as  are  liquid  particles.  If  the  virus  does  diffuse  in  all  direc- 
tions like  a  gas,  the  intensity  of  the  infection  should  diminish 
according  to  the  square  of  the  distance,  which  it  did  not  do 
at  Fulham  and  Liverpool.  Whether  it  diffuses  or  is  carried 
like  solid  particles,  the  houses  nearest  th(^  hospital  should  be 
by  far  the  most  intensely  infected.  Solid  particles  are  speed- 
ily, under  ordinary  conditions,  precipitated  to  the  ground,  as 
one  may  easily  note  by  observing  a  cloud  of  dust  of  any  kind. 
The  particles  of  smallpox  virus  ought,  then,  to  work  their 
chief  havoc  close  to  the  hospital.  Yet  this  incidence  was  not 
always  the*  case,  even  at  Fulham,  and  similar  absence  of  near-by 


INFECTION  BY  AIR  267 

infection  was  noted  at  StockwelP  and  Liverpool.'  Again, 
quite  a  number  of  Instances  are  given  where  large  institu- 
tions, like  schools,  workhouses  and  general  hospitals,  have 
been  located  within  the  area  alleged  to  have  been  severely- 
infected  from  the  hospital,  and  yet  have  nearly  or  entirely 
escaped.  It  is  curious,  too,  that  in  the  only  instance  I  have 
noticed  in  which  the  sex  of  the  patients  in  the  infected  area 
was  given,  namely  Fulham,^  twenty-four  were  male  and 
seventeen  female.  As  so  many  more  men  are  away  from  their 
homes  at  work,  a  much  larger  female  population  must  be 
exposed  to  the  hospital  influence,  and  the  female  patients 
ought  to  be  more  numerous  than  the  male.  In  most  out- 
breaks of  smallpox  the  male  patients  are  more  numerous, 
because  the  men  move  about  more,  and  are  thus  more  likely 
to  be  exposed  to  cases  of  disease.  Again,  it  is  remarkable 
that  extension  should  be  more  likely  to  take  place  from 
acute  than  from  chronic  cases.  In  the  former  it  is  probable 
that  the  moist  mucous  membrane  is  the  only  source  of  infec- 
tion, while  in  the  latter  the  dried  crusts  are  known  to  be 
infectious. 

Distribution  of  Cases  Opposed  to  Theory.  —  It  is  thus  seen 
that  there  are  a  number  of  facts  and  a  number  of  theoretical 
considerations  opposed  to  the  theory  of  aerial  transmis- 
sion. That  smallpox  is  distributed  with  decreasing  inten- 
sity around  smallpox  hospitals  is  not  a  demonstration  that 
the  hospital  is  the  cause,  for  as  even  the  advocates  of  the 
theory  admit,  such  circles  of  infection  can  be  drawn  around 
other  points  in  a  city  during  epidemic  times,  as  was  indeed 
shown  by  Hope  in  Liverpool  in  1902-03  and  Clayton  at  Gates- 
head in  1903-04.  In  fact  most  outbreaks,  not  only  of  small- 
pox but  also  of  scarlet  fever  and  diphtheria,  are  in  a  general  way 
arranged  around  a  center,  with  more  cases  toward  the  center 

*  Rep.  Roy.  Com.,  Smallpox  and  Fever  Hospitals,  Lond.,  1882,  92. 

*  Hope,  Observations  by  the  Med.  Off.  Health  on  the  Report  of 
Dr.  Reece  on  Smallpox  at  Liverpool.     C.  Tinling  &  Co.,  1905,  11. 

»  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  Lond.,  1880-81,  X,  Supl. 


268        THE  SOURCES  AND  MODES  OF  INFECTION 

and  fewer  toward  the  periphery.  It  is  not  remarkable  that 
occasionally  a  smallpox  hospital  is  found  near  the  center  of 
such  a  localization  of  disease.  As  favoring  this  chance,  it  must 
be  remembered  that  the  population  near  a  smallpox  hospital 
is  likely  to  be  of  the  poorer  classes,  upon  whom  the  weight  of 
this  disease  most  often  falls.  That  surrounding  outbreaks 
occur  chiefly  after  the  hospital  has  been  occupied,  is  only  to 
be  expected,  as  the  hospital  is  occupied  by  a  number  of  cases 
only  in  epidemic  times.  Much  stronger  evidence  would  be 
offered  by  the  advocates  of  this  theory  if  they  could  show 
that  no  other  explanation  of  the  origin  of  the  cases  could  be 
found  than  hospital  infection.  This  they  are  not  able  to  do, 
and  in  the  absence  of  such  evidence,  and  in  the  face  of  the 
evidence  against  the  theory,  the  theory  must  be  considered 
not  demonstrated. 

Cases  often  traced  to  Other  Sources.  —  A  good  deal  of 
evidence  in  regard  to  the  influence  of  hospitals  in  the  spread 
of  smallpox  was  collected  in  England  at  a  time  when  there 
was  no  registration  of  the  disease,  when  the  frequency  and 
importance  of  mild  cases  were  not  recognized  as  at  present, 
and  when  its  administrative  control  was  not  so  complete. 
Thus  it  was  stated  that  many  cases  of  smallpox  walked  to 
the  Homerton  Hospital  to  apply  for  admission,  ambulance 
drivers  stopped  at  public  houses,  children  of  the  neigh- 
borhood rode  on  the  steps  of  the  ambulance  and  the  patient's 
friends  inside.  It  would  not  be  surprising  if,  under  such  con- 
ditions, smallpox  spread  by  contact — and  indeed  it  was  admit- 
ted that  this  was  a  factor.  It  is  interesting  to  note  that  even 
Power  found  personal  exposure  the  cause  of  nine  out  of  thirty- 
two  cases  near  Fulham.  In  many  outbreaks,  where  there  is 
no  question  at  all  of  hospital  infection,  to  trace  the  source  of 
such  a  proportion  of  cases  is  all  that  can  be  expected.  Again, 
in  the  block  of  houses  nearest  the  same  Fulham  Hospital 
Dudfield  ^  showed  that  twenty  of  forty-one  cases  were  due  to 

1  Dudfield,  lU'p.  Roy.  Corn.,  Smallpox  and  Fever  Hospitals,  Lond., 
1882,  101. 


INFECTION  BY  AIR  269 

contact  infection.  According  to  Clayton,^  the  medical  officer 
of  health  of  Gateshead,  of  the  fifty-six  cases  of  smallpox 
within  one-half  mile  of  the  hospital,  on  which  Buchanan  bases 
his  conclusion  that  the  disease  was  carried  by  the  air,  fifty- 
two  were  traced  to  contact  infection.  Clayton  in  his  report 
on  this  outbreak  very  clearly  shows  the  fallacy  of  most  of 
the  arguments  presented  by  Buchanan.  In  Liverpool  it  was 
shown  by  the  advocates  of  aerial  transmission  that  within 
one-quarter  of  a  mile  of  the  Parkhill  Hospital  the  rate  of 
incidence  of  smallpox  was  five  hundred  and  twenty-six  per  ten 
thousand  houses,  while  in  the  city  outside  of  hospital  areas 
it  was  only  eighty-five.  A  detailed  study  shows  that  this 
apparent  high  rate  depended  on  only  nine  patients  in  one 
hundred  and  seventy-one  houses,  and  Hope  shows  that  of  these 
nine,  four  were  known  to  be  due  to  direct  exposure  to  other 
cases.  A  careful  study  of  the  report  by  Reece "  of  this  Liver- 
pool outbreak  is  well  worth  while  by  all  interested  in  this 
subject.  A  most  ingenious  use  has  been  made  of  the  facts, 
but  an  impartial  critic  must  see  that  the  conclusions  arrived 
at  are  entirely  unwarranted.  If  one  is  still  in  doubt,  he  should 
read  the  report  of  Hope,^  the  medical  officer  of  health  of 
Liverpool,  which  clearly  and  briefly  refutes  all  the  arguments 
of  the  government  inspector. 

Conclusions  concerning  Smallpox.  —  It  appears  that  the 
evidence  for  the  aerial  transmission  of  smallpox  from  hospi- 
tals consists  solely  of  the  alleged  distribution  of  the  disease, 
at  a  gradually  decreasing  rate,  around  the  hospital,  the  exist- 
ence of  the  cases  being  assumed  to  be  otherwise  unexplained. 
It  will  be  noted : 

1.  That  there  are  comparatively  few  instances  of  such  dis- 
tribution recorded. 

'  Clayton,  J.  Roy.  San.  Ins.,  1905,  XXVI,  199. 

^  Reece,  Rep.  Local  Gov.  Bd.,  Lond.,  No.  208,  Smallpox  in  Liverpool, 
1905. 

'  Hope,  Observations  by  the  Med.  Off.  Health  on  the  Report  of 
Dr.  Reece  on  Smallpox  at  Liverpool.    C.  Tinling  &  Co.,  Liverpool,  1905. 


270         THE  SOURCES  AND  MODES  OF  INFECTION 

2.  That  many  instances  are  noted  where  there  was  no  such 
diffusion. 

3.  That  in  some  of  the  alleged  instances,  as  at  Fulham, 
Gateshead  and  Liverpool,  a  large  number  of  the  surrounding 
cases  have  been  shown  to  be  due  to  contact  infection. 

4.  That  in  the  long  run  the  amount  of  infection  around 
the  hospital  should  diminish  according  to  the  square  of  the 
distance.  This  it  does  not  do,  Ijut  it  diminishes  irregularly, 
just  as  it  does  in  most  outbreaks  of  this  and  other  diseases 
due  to  contact  infection. 

5.  There  may  sometimes  be  contact  infection  from  the  hos- 
pital. The  surrounding  population  is  often  of  the  poorer  sort, 
and  is  consequently  particularly  subject  to  the  disease. 
Contact  infection  and  chance  may  be  sufficient  to  account 
for  those  instances  where  a  smallpox  hospital  is  the  center 
of  a  local  outbreak. 

The  evidence  in  favor  of  the  aerial  transmission  of  small- 
pox from  hospitals  is  so  slight  that  it  should  never  influence 
a  municipality  in  its  selection  of  a  hospital  site. 

Chicken  Pox.  —  Caigcr,^  while  able  successfully  to  isolate 
scarlet  fever,  diphtheria  and  whooping  cough  in  his  hospital 
wards  b}^  the  cubicle  .system,  had  several  transfers  of  chicken 
pox,  and  concludes  from  his  experience  that  this  disease  is 
frequently  air-borne.  Others  in  England  and  in  the  United 
States  have  had  difficulties  in  isolating  chicken  pox.  Good- 
all,^  however,  has  isolated  this  disease  in  cubicles  with  only 
1  cross  infection  which  he  does  not  think  was  air-borne. 

Scarlet  Fever  believed  to  be  Air-borne.  —  Scarlet  fever  also 
is  generally  believed  to  be  an  air-borne  disease.  One  reason 
for  this  is  doubtless  because  until  recently''  the  desquamating 
epidermis  was  considered  to  be  the  chief  vehicle  of  infection. 
As  the  epidermis  comes  off  to  a  large  extent  as  very  fine  light 
particles,  it  was  but  natural  to  assume  that  these  would  be 
'  Rep.  Motropol.  Asylums  Bd.,  1907,  1908. 
«  Pub.  IloalUi,  l.on<l.,  1911-12,  XXV,  17. 


INFECTION  BY  AIR  271 

readily  carried  by  the  air.  Recently  much  clinical  evidence 
has  accumulated  which  indicates  that  the  epidermal  scales 
are  not  infectious,  and  this  has  in  turn  developed  doubts  as 
to  the  disease  being  commonly  air-borne.  Whether  or  not 
the  epidermis  is  infectious,  there  seems  to  be  no  really  good 
evidence  that  the  disease  is  caused  by  air-borne  infection.  On 
the  contrary,  there  is  considerable  evidence  that  it  is  not  air- 
borne. 

Scarlet  Fever  in  Hospitals.  —  The  writer,  like  every  health 
officer,  has  frequently  noted  that  a  case  of  this  disease  may 
remain  in  school  or  hospital  ward  for  days,  or  sometimes  for 
weeks,  without  another  case  developing,  or  at  most  only  one 
or  two  cases.  Such  facts  indicate  that  the  disease  is  not 
easily  air-borne.  Visitors  to  fever  hospitals  do  not  contract 
scarlet  fever.  Thus,  of  three  hundred  to  four  hundred  non- 
immune students  who  visited  the  scarlet-fever  wards  of  the 
Philadelphia  hospital,  remaining  in  the  ward  from  twenty 
minutes  to  an  hour,  not  one  contracted  the  disease.^  Often- 
times scarlet  fever  does  attack  other  patients  in  hospitals, 
but  it  is  in  a  manner  to  indicate  contact  rather  than  air-borne 
infection.  When  contact  infection  is  rigidly  guarded  against, 
as  in  the  Pasteur  Hospital  in  Paris  and  in  many  English 
hospitals,  scarlet  fever  may  be,  and  is,  treated  in  the  same 
ward  with  other  diseases  without  cross  infection.  The  failure 
of  contagious  disease  to  spread  in  hospitals  when  contact 
infection  is  guarded  against  was  referred  to  in  some  detail 
in  the  chapter  on  contact  infection,  and  is  a  striking  demon- 
stration of  the  small  part  played  by  aerial  infection  in  the 
transmission  of  the  common  contagious  diseases. 

Scarlet  Fever  in  Dwellings.  —  I  have  been  much  impressed 
by  the  fact  that  scarlet  fever  and  likewise  diphtheria  do  not 
extend  from  one  family  to  another  in  the  same  house.  Most 
people  in  Providence  live  in  houses  of  two  or  three  stories, 
rarely  more,  with  one  or  two  families  on  each  floor.     Of  4306 

'  Welch  and  Schamberg,  Acute  Infectious  Diseases,  Phila.,  1905, 
346. 


272         THE  SOURCES  AND  MODES  OF  INFECTION 

"  other  families  "  living  in  the  same  house  with  scarlet-fever 
families,  only  6.8  per  cent  were  invaded.  Investigation  has 
shown  that  with  very  few  exceptions  the  infection  takes  place 
through  close  intercourse  before  the  disease  is  recognized  or, 
more  rarely,  after  the  isolation  has  been  terminated.  Most 
of  the  disease  in  the  "other  families  "  develops  within  a  few 
days  after  the  report  of  the  primary  case,  and  is  doubtless 
due  to  contact  infection  before  the  disease  is  recognized. 
Between  the  end  of  the  second  week  and  the  termination  of 
isolation,  the  disease  extends  to  other  families  in  the  house 
in  only  0.6  per  cent  of  the  cases,  and  in  most  of  these  it  is 
known  that  isolation  is  not  carried  out,  and  that  there  is  free 
intercourse  between  the  families.  If  the  disease  were  air- 
borne, it  would  certainly  pass  from  one  family  to  another  in 
the  house,  which  it  does  not  do. 

Scarlet  Fever  and  Outdoor  Air.  —  If  scarlet  fever  is  not 
air-borne  from  family  to  family  in  the  house,  one  would  not 
expect  it  to  be  borne  from  house  to  house  by  the  air.  Yet 
such  a  claim  is  sometimes  made,  and  even  that  the  virus  of 
the  disease  may  thus  be  transmitted  a  considerable  distance. 
A  number  of  the  reports  of  the  health  department  of  Phila- 
delphia contain  shaded  maps  purporting  to  show  an  excess 
of  this  disease,  as  well  as  of  smallpox,  in  those  parts  of  the 
city  near  the  hospital.  I  do  not  think  that  much  value  at- 
taches to  such  maps,  for  there  are  too  many  factors  involved, 
and  very  rarely  is  the  intensity  of  the  disease  as  great  close 
to  the  hospital  as  the  theory  demands.  Moreover,  around 
very  many  hospitals  no  such  distribution  of  the  disease  can 
be  shown.  Thus  Tarnissicr,^  in  Paris,  found  that  the  En- 
fants  Malades  and  Trousseau  hospitals  could  not  be  con- 
sidered foci  of  infection.  The  same  is  true  of  the  scarlet-fever 
wards  in  Providence,  in  Detroit  and  in  Boston.  In  the  latter 
city,^  for  the  period  studied,  there  were  no  cases  of  the  disease 
within  one-eighth  of  a  mile  of  the  hospital,  while  in  the  next 

'  Turnissier,  Somainc  mod.,  1903,  207. 

2  Med.  and  Surg.  Kc-p.,  Bost.  City  Hosp.,  1897. 


INFECTION  BY  AIR  273 

eighth  of  a  mile  circle  there  were  sixty-eight  cases,  in  the  next 
seventy-one,  in  the  next  seventy-five  and  in  the  next  seventy- 
two. 

,  Where  various  contagious  diseases  are  treated  in  different 
wards  of  the  same  hospital  there  is  sometimes  cross  infection. 
But  this  occurs  so  irregularly  as  to  time  and  place,  and  is  so 
limited  in  amount,  that  it  can  scarcely  be  attributed  to  any- 
thing but  contact  infection.  As  most  of  the  physicians  and 
nurses  in  our  contagious  hospitals  have  no  appreciation  of 
what  true  medical  asepsis  really  means,  it  is  surprising  that 
we  see  as  little  cross  infection  as  we  do.  If  scarlet  fever  does 
not  spread  within  the  walls  of  the  Pasteur  Hospital,  it  would 
indeed  be  marvelous  if  it  should  extend  to  the  neighl^oring 
houses.  If  it  does  not  pass  from  family  to  family  in  the  same 
house,  it  would  be  most  surprising  if  it  could  be  wafted  by  the 
air  over  large  areas  around  the  Philadelphia  Hospital. 

Diphtheria  and  Sewer  Air.  —  Diphtheria  was  formerly  be- 
lieved to  be  a  filth  disease,  and  it  was  also  believed  that  air, 
especially  sewer  air,  was  frequently  the  vehicle  of  infection. 
Graham-Smith  refers  to  this,^  and  shows  that  there  is  no 
foundation  for  this  l^elief,  and  that  diphtheria  bacilli  have 
never  been  found  in  sewer  air.  He  says  that  Shattock  culti- 
vated bacilli  of  low  virulence  in  sewer  air  for  two  months,  but 
could  not  thereby  increase  their  virulence.  As  I  was,  years 
ago,  prejudiced  in  favor  of  the  filth  origin  of  this  disease,  I 
gave  the  matter  careful  consideration  in  my  investigation  of 
cases,  but  was  never  able  to  find  any  evidence  that  sewer  gas 
was  an  etiological  factor.  Indeed  my  observation  of  diph- 
theria and  typhoid  fever  had  as  much  to  do  with  my  dis- 
carding the  filth  and  sewer-gas  theories  as  had  the  slowly 
accumulating  mass  of  bacteriological  evidence. 

Diphtheria  in  Hospitals  and  Dwellings.  —  From  an  epi- 
demiological standpoint  diphtheria  and  scarlet  fever  are  much 
alike.     As  the  latter  disease  has  been  supposed  to  be  air- 

^  Nuttall  and  Graham-Smith,  The  Bacteriology  of  Diphtheria, 
Cambridge,  1908,  321. 


274         THE  SOURCES  AND  MODES  OF  INFECTION 

borne  from  person  to  person,  so  has  the  former,  and  there  is 
the  same  lack  of  positive  evidence  for  both  diseases;  and  the 
evidence  against  the  theory  is  much  the  same  for  diphtheria 
as  for  scarlet  fever.  As  is  stated  by  Graham-Smith,  bacterio- 
logical evidence  is  all  against  diphtheria  being  an  air-borne 
disease  except  in  rare  instances,  yet  probably  most  medical 
men  and  most  health  officers  consider  that  the  disease  is 
commonly  spread  in  this  way.  But  visiting  students  in  hos- 
pital wards  do  not  contract  it,  and  it  does  not  spread  when 
cases  of  this  disease  are  treated  in  pavilions  together  with 
other  diseases.  In  Providence  I  am  certain,  from  a  careful 
study  of  about  eleven  thousand  cases,  that  it  practically  never 
extends  from  one  family  to  another  in  a  house  except  by  per- 
sonal contact ;  and  it  does  not  extend  from  one  hospital  ward 
to  another  through  the  air.  At  North  Brother  Island  in  New 
York  there  is  a  diphtheria  ward  only  a  few  feet  from  a  tuber- 
culosis ward,  and  Dr.  S.  A.  Knopf  tells  me  that  there  is  no 
cross  infection.  Similar  conditions  are  noted  in  many  other 
hospitals.  Yet  Coutts^  recently  suggested,  without  any  evi- 
dence, that  certain  cases  of  diphtheria  were  due  to  street  dust, 
and  Cornell"  attempted  to  show  that  the  development  of  the 
disease  in  a  certain  locality  in  Philadelphia  was  due  to  air- 
borne infection.  At  best  there  was  in  the  instances  reported 
by  the  latter  only  a  possibility  of  aerial  infection,  with  the 
probabilities  very  much  against  it,  while  the  facts  as  stated 
did  point  very  strongly  to  the  existence  of  unrecognized  cases 
probal^ly  spreading  the  disease  by  contact. 

Typhoid  Fever  and  Sewer  Air.  —  During  the  heyday  of 
the  sewer-gas  theory  of  disease,  numerous  outbreaks  of 
typhoid  fever  were  supposed  to  hav(i  been  traced  to  infection 
by  means  of  air  from  sewers  and  drains.  A  number  of  typical 
reports  are  given  by  Roechling,^  and  others  may  be  found 
scattered  through  medical  literature.     In  none  of  these  is  real 

1  Coutts,  Pub.  TTnulth,  Lond.,  lOOG-O?,  XIX,  297. 

2  Cornell,  N.  York  M.  J.  |ole.|,  VM)f>,  LXXXII,  1318. 

'  Roechling,  Sewer  (Jius  und  Health,  Loud.  &  N.Y.,  1898,  30. 


INFECTION  BY  AIR  275 

proof  given  that  the  disease  was  thus  caused;  it  was  merely 
a  plausible  hypothesis.  Now  in  the  light  of  present-day 
knowledge  of  bacteria  and  sewer  air  it  is  no  longer  a  plausible 
hypothesis.  For  years  past  we  have  been  able  to  trace  most 
of  our  outbreaks  of  this  disease  to  water,  milk,  oysters  or 
other  food,  or  to  contact  infection.  In  most  instances  they 
could  not  be  due  to  sewer  air.  Usually  investigation  shows 
that  house  or  institution  outbreaks  cannot  possibly  be  due 
to  sewer  air,  and  where  such  an  hypothesis  is  permissible,  it 
usually  appears  highly  improbable.  I  see  almost  every  year 
small  house  outbreaks  of  typhoid  fever.  There  is  rarely  any 
evidence  of  the  escape  of  drain  air  into  the  house,  and  in 
almost  all  instances  such  escape  is  impossible.  Most  of  these 
house  outbreaks  indicate  contact  infection,  and  in  none  can 
contact  infection  be  excluded.  I  have  never  seen  the  slightest 
evidence  that  typhoid  fever  is  ever  due  to  sewer  air,  though  I 
began  my  public-health  work  with  a  fairly  strong  belief  in 
the  danger  from  this  source  and  sought  diligently  for  evi- 
dence of  it. 

Typhoid  Fever  and  Dust.  —  It  is  also  claimed  that  infected 
dust  may  be  the  cause  of  outbreaks  of  this  disease.  This 
mode  of  infection  was  considered  to  be  of  some  moment  in 
the  Spanish- American  and  Boer^  wars,  and  certainly  bacterio- 
logical evidence  points  to  its  possibilit3\  Many  outbreaks  sup- 
posed to  be  due  to  dust  infection  have  been  reported.  Some 
of  these  are  referred  to  by  Germane^  and  Visbecq'  and  in  the 
Report  on  Typhoid  Fever  in  the  war  with  Spain, ^  but  if  the 
original  reports  of  these  outbreaks  are  examined  it  will  be  seen 
that  the  evidence  is  very  weak  indeed.     Because  the  houses 

'  Tooth,  Brit.  M.  J.,  Lond.,  1900,  II,  136S;  Tr.  Clin.  Soc,  XXXIV, 
1213. 

^  Germano,  Ztsclir.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1897,  XXIV, 
403. 

^  Visbecq,  Arch,  de  med.  et  pharm.  miht.,  Par.,  1903,  XLI,  536. 

*  Abst.  of  Rep.  on  the  Origin  and  Spread  of  Typhoid  Fever  in  U.  S. 
Military  Camps  during  the  Spanish  War  of  1898,  Wash.,  1900,  215. 


276       THE  SOURCES  AND  MODES  OF  INFECTION 

or  apartments  or  barracks  where  an  excess  of  typhoid  fever 
appears  are  situated  not  far  from  a  place  where  possibly 
infected  feces  are  deposited,  it  is  argued  that  the  disease  is 
caused  by  the  wind  blowing  over  the  spot  alleged  to  be  in- 
fected. Quill  ^  reports  that  typhoid  fever  was  brought  to  a 
certain  garrison  in  India  by  a  company  of  five  thousand  Boer 
prisoners,  many  of  whom  were  infected.  The  disease  con- 
tinued to  spread  among  the  prisoners  for  three  months,  until 
there  were  from  six  to  eight  hundred  cases.  Then  it  slowly 
appeared  among  the  garrison,  until  there  were  twenty-four 
cases.  It  was  supposed  to  be  caused  by  dust  blown  from  the 
latrines,  though  the  possibility  of  fly-borne  infection  is  men- 
tioned; but  an  extraneous  source,  or  unsuspected  contact 
infection,  is  highly  probable,  though  neither  is  excluded  or 
even  mentioned.  Mewius  "  gives  an  excellent  report  of  what 
he  considers  an  air-borne  outbreak,  but  it  appears  rather  to 
have  been  due  to  contact  infection,  a  typical  outbreak  of 
what  Winslow  calls  prosedemic  infection. 

The  fact  that  typhoid  fever,  dysentery  and  cholera^  can 
be  treated  in  a  well-managed  hospital  without  spreading  to 
other  patients  is  good  evidence  that  these  diseases  are  not 
air-borne  under  such  circumstances. 

Infantile  Diarrhea  and  Dust.  —  Newsholme,^  judging 
largely  from  the  fact  that  the  summer  diarrhea  of  infants 
occurs  with  greater  frequency  during  dry  seasons,  and  in 
towns  with  poor  scavenging,  infers  that  it  is  due,  to  some 
extent  at  least,  to  the  infection  of  milk  and  other  foods  by 
dust.  This  also  is  the  view  of  Hope,'^  who  states  that  in 
Liverpool  in  six  Septembers  with  an  average  rainfall  of  13.8 
inches  there  wore  373  deaths  from  diarrhea,  while  in  four- 

1  Quill,  Brit.  M.  J.,  Loncl.,  1902,  I,  383. 

'  Mewius,  Ztschr.  f.  Hyg.  u.  Infcctionskrankh.,  Lcipz.,  189G,  XXIII, 
497. 

»  Woodruff,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  1160. 
*  Newsholinc,  Pub.  Health,  Lond.,  1S99-1900,  XII,  139. 
'  Hope,  Pub.  Health,  Loud.,  1S9S-99,  XI,  435. 


INFECTION  BY  AIR  217 

teen  Septembers  with  10.9  inches  of  rain  the  deaths  num- 
bered 573. 

Influenza.  —  During  the  present  pandemic  of  influenza, 
especialh'  at  its  commencement,  it  was  frequently  stated  that 
the  disease  was  chiefly  air-borne,  and  air-borne  to  great  dis- 
tances, even  across  the  Atlantic.  This  view  prevailed  be- 
cause the  disease  spread  with  such  great  rapidity,  appearing 
on  this  side  of  the  Atlantic  at  about  the  same  time  that  it 
did  in  England,  and  developing  almost  simultaneously  in  a 
large  number  of  localities.  The  subject  has  been  thoroughly 
studied  by  Leichtenstern,^  Parsons "  and  Schmid.  The  lat- 
ter's  observations  were  in  Switzerland  chiefly,  where  he  had 
ample  opportunity  to  study  the  outbreak  in  small  isolated 
communities.  His  work  is  reviewed  by  Leichtenstern,  who 
states  that  the  disease  never  developed  except  after  the  ad- 
vent of  some  stranger.  Parsons  studied  the  incidence  of  the 
disease  on  several  thousand  deep-sea  fishermen  and  on  four 
hundred  offshore  lighthouse  keepers,  and  in  no  instance  did 
the  disease  develop  except  as  the  result  of  contact  with  the 
sick  or  within  two  or  three  days  after  leaving  shore.  He 
says  there  is  no  evidence  whatever  that  the  disease  is  air- 
borne. Leichtenstern  studied  the  extension  of  the  disease  to 
distant  countries,  and  found  that  all  the  evidence  pointed  to 
personal  contact  as  the  only  factor  in  its  spread.  Thus  care- 
ful epidemiological  investigation  is  entirely  in  accord  with 
the  findings  of  bacteriology,  for  the  weak  resistance  of  the 
bacillus  makes  it  difficult  to  understand  how  the  disease  can 
be  carried  by  the  air  as  readily  as  is  often  alleged.  This 
feebleness  of  the  germ  renders  it  unlikely  that  influenza  is 
a  dust-borne  disease.  Of  course  it  may  spread  by  droplet 
infection,  but  the  increased  volume  of  the  secretions,  the  per- 
sistence of  the  bacillus  after  recovery  and  the  great  number 
of  carriers  give  such  opportunities  for  contact  infection  that 

^  Leichtenstern,  Nothnagel's  Encycl.  Pract.  Med.,  Influenza,  Phila. 
and  Lond.,  1905,  523. 

^  Parsons,  Brit.  M.  J.,  Lond.,  1891,  II,  303. 


278       THE  SOURCES  AND  MODES  OF  INFECTION 

it  is  hardly  necessary  to  attribute  much  importance  to 
aerial  infection,  as  the  term  is  generally  used,  or  to  fomites 
infection. 

Poliomyelitis.  —  Hill,^  from  a  careful  study  of  this  disease 
in  Minnesota,  was  led  to  suggest  the  theory  that  this  might 
be  a  dust -borne  disease.  He  finds  that  usually  outbreaks  occur 
in  hot,  dry  weather,  and  many  cases  had  long  exposure  to  dust 
infected  with  animal  feces,  especially  those  of  the  horse. 
Hill  says  that  at  Winona  and  some  other  places  the  disease 
ceased  soon  after  the  watering  of  the  roads  was  begun. 
The  fact  that  poliomyelitis  occurs  chiefly  in  the  driest 
season  of  the  year  has  led  some  others  to  accept  Hill's 
proposition,  and  some  have  made  similar  observations  as  to 
the  checking  of  outbreaks.  Hillier-  reports  an  outbreak 
at  Stowmarket,  Eng.,  brought  to  a  sudden  stop  by  the 
watering  of  streets.  Experiments  indicate  that  the  virus 
has  considerable  resistance  and  may  possibly  be  transported 
by  dust.  Landsteiner,  Levaditi  and  Pastia^  found  that  it 
was  virulent  after  being  dried  thoroughly  for  24  days, 
Neustadter  and  Thro  ^  in  at  least  one  instance  succeeded  in 
causing  the  disease  in  a  monkey  by  inoculating  dust  from  a 
room  occupied  by  a  case  of  the  disease.  Fifty  grams  of 
dust  were  shaken  up  with  30  c.c.  of  water  and  5  c.c.  of  the 
filtrate  were  used  for  the  experiment. 

Measles.  —  Measles  is  considered  a  typical  air-borne 
disease,  at  least  within  doors,  but  the  experience  of  the 
Parisian  hospitals^  shows  that  the  danger  of  infection  within 
wards  decreases  as  the  opportunity  for  contact  infection  is 

'  Hill,  Northwestern  Lancet,  Sept.  1,  1909  [reprint]. 

2  Hillier,  Med.  Oil.,  1912,  VII,  78. 

'  Landsteiner,  Levaditi  and  Pastia,  Ann.  de  I'lnst.  Pasteur,  Par., 
1911,  XXV,  80.5. 

*  Neustadter  and  Thro,  N.  York  M.  J.,  1911,  XCIV,  614. 

^  Grancher,  Cong.  Internat.  de  m6d.,  1900,  XIII,  C.-r.,  Par.,  Sect. 
de  med.  de  I'enfanee,  478.  Moizard,  Bull,  et  mem.  Soc.  med.  d.  hop. 
de  Par.,  1900,  3  s.,  XVII,  (iS.'J.  Martin,  Rev.  d'hyp;.,  Par.,  1903,  XXV, 
250;  Bull,  et  uiem  Soc.  med.  d.  hop.  de  Par.,  1904,  3  e.,  XXI,  297. 


INFECTION  BY  AIR  279 

lessened.  Grancher  was  the  first  to  avowedly  disregard 
infection  by  air  and  to  attempt  to  control  the  spread  of 
disease  by  strict  attention  to  medical  asepsis.  At  I'ho- 
pital  des  Enfants-Malades  he  did  not  at  first  use  cubicles 
but  merely  wire  screens  or  low  partitions  between  the  beds. 
During  the  10  years  when  this  experiment  was  going  on 
measles  was  introduced  139  times  and  from  these  cases  115 
cross  infections  resulted,  less  than  one-third  as  many  as 
occurred  when  attention  was  not  focused  on  the  prevention 
of  contact  infection.  A  suggestive  instance  is  reported  of  a 
child  with  measles  who  remained  for  24  hours  in  an  open 
ward  with  many  susceptibles,  and  it  is  stated  that  in  the 
3  cases  which  later  developed  there  had  been  contact  with 
the  first  patient,  either  direct,  or  by  freshly  infected  fomi- 
tes.  At  the  Pasteur  Hospital  126  cases  of  measles  were 
cared  for  without  a  single  cross  infection.  At  the  Provi- 
dence City  Hospital  which  was  opened  in  March,  1910, 
many  different  diseases  are  cared  for  in  rooms  open  most 
of  the  time  into  a  common  corridor  as  in  the  Pasteur  Hos- 
pital, while  other  mixed  cases  are  "  barriered  "  in  other 
wards,  as  described  on  pages  200  to  202.  Up  to  September, 
1911,  56  cases  of  measles  had  been  admitted,  with  extension 
in  only  one  instance  to  one  child. ^  Since  then  there  have 
been  two  small  outbreaks  which  Richardson  thinks  were 
most  likely  not  due  to  aerial  infection  but  to  some  failure 
in  technique.  One  of  these  outbreaks  arose  from  a  single 
case,  though  at  other  times  several  cases  had  been  cared  for 
at  one  time  without  extension.  In  this  outbreak  one  of 
the  cases  was  on  a  different  floor  from  the  infecting  case. 
Rohmer^  from  his  hospital  experience  at  Cologne  is  satisfied 
that  measles  is  not  air-borne  further  than  between  adjoin- 
ing beds. 

English  Hospital  Experience.  —  Most  English  hospital 
superintendents  who  have  tried  cubicles  and  barriers  do 

1  Richardson,  Internat.  Hosp.  Rec,  1911,  XV,  18. 

^  Rohmer,  Jahrb.  f.  Kinderheilkunde,  1912,  LXXV,  78. 


280   THE  SOURCES  AND  MODES  OF   INFECTION 

not  think  that  measles  can  be  safely  treated  in  this  way 
because  they  consider  it  likely  to  be  air-borne,  or  that  is 
the  explanation  offered  by  some  at  least.  Caiger,^  Thom- 
son,2  Goodall,^  Gordon^  and  Biernacki^  may  be  mentioned 
as  holding  this  view  in  regard  to  measles  and  chicken  pox. 
All  these  and  Crookshank®  do  not  find  that  diphtheria  is 
air-borne  under  the  hospital  conditions  mentioned  and 
uncomplicated  scarlet  fever  usually  is  not.  Caiger  does 
not  think  that  rubella  and  whooping  cough  are  readily 
air-borne,  while  Thomson  is  inclined  to  think  that  they  are. 
Biernacki  agrees  with  Caiger  as  to  rubella  and  also  as  re- 
gards whooping  cough,  if  the  beds  are  at  least  12  feet  apart 
so  as  to  prevent  droplet  infection  in  coughing.  Even  then 
he  usually  employs  a  canopy  as  an  additional  precaution. 
Biernacki  thinks  that  ring-worm  is  readily  air-borne. 
This  also  is  the  view  held  by  Gates  from  a  study  of  this 
disease  in  schools.'' 

Just  as  this  is  going  to  press  an  article  by  Rundle  and 
Burton^  has  appeared  reporting  two  years'  experience  with 
a  hospital  ward  at  Liverpool  in  which  a  variety  of  infectious 
and  non-infectious  cases  were  cared  for  without  any  at- 
tempt at  air  isolation.  In  all,  668  persons  passed  through 
the  ward,  of  whom  69  had  scarlet  fever,  40  diphtheria,  37 
measles,  38  varicella,  9  whooping  cough  and  215  erysipelas. 
There  were  only  2  cross  infections,  1  of  diphtheria  and  1 
of  scarlet  fever.  These  authors  believe  that  in  hospital 
wards  the  "  danger  of  aerial  infection  is  to  be  disregarded 
for  practical  purposes." 

1  Caiger,  Rep.  Metropol.  Asylums  Bd.,  1907,  1908,  258;  Med. 
Officer,  1910,  V.,  7G. 

*  Thomson,  Rep.  Metropol.  Asylums  Bd.,  1908,  201;  Med.  Officer, 
1910,  V,  197. 

»  Goodall,  Rep.  Metropol.  Asylums  Bd.,  1910,  257. 

*  Gordon,  Hop.  on  Health  of  Manchester,  1908,  154. 
^  Biernacki,  Tlie  Nursing  Times,  1908. 

*  Crookshank,  l']ssays  and  (Clinical  Studios,  T^ond.,  1911,  134. 

7  Cates,  Pul).  Health,  Lond.,  1910-11,  22G. 

8  Ruudlc  and  Burton,  Lancet,  Lond.,  1912,  I,  720. 


INFECTION  BY  AIR  281 

Typhus  Fever  not  Air-Bome.  —  As  will  be  shown  in 
Chapter  VIII,  it  is  quite  probable  that  typhus  fever  is 
transmitted  by  insects  exclusively.  But  whether  this  is  so  or 
not,  the  successful  management  of  this  disease  in  the  same 
wards  with  other  patients  in  Edinburgh,  in  Liverpool  and  in 
Mexico  City  indicates  that  it  is  not  an  air-borne  disease. 

Pneumonic  Plague.  —  The  extensive  outbreak  of  plague 
in  Manchuria  in  1910  attracted  much  attention,  since 
rodents,  while  perhaps  furnishing  the  original  infection, 
played  little  part  in  the  extension,  as  it  seemed  to  be  spread 
almost  exclusively  from  person  to  person.  Kitasato,^  if 
reported  correctly,  concluded  that  the  disease  could  not 
be  air-borne  but  is  caused  "  by  coming  in  close  contact 
with  plague  victims  and  by  sputa."  That  droplet  infection 
is  of  great  importance  in  this  type  of  the  disease  cannot  be 
doubted  and  was  amply  demonstrated  by  Strong.^  In  a 
preliminary  note  he  reports  experiments  in  which  15  of  39 
plates  held  in  front  of  coughing  patients  were  infected 
with  virulent  bacilli.  He  says  that  the  air  throughout  the 
ward  was  infected,  though  the  experiments,  as  reported,  do 
not  seem  to  furnish  proof  of  this.  Respirators  are  said 
to  have  been  used  successfully  in  avoiding  infection  by 
physicians  and  others  in  close  contact  with  the  patients. 
No  real  evidence,  however,  seems  to  have  been  advanced  to 
show  that  the  disease  was  air-borne  other  than  by  droplets. 

Infection  by  Air  not  Impossible.  —  Since  the  development 
of  bacteriology,  evidence  has  been  accumulating  to  show 
that  the  air  as  a  vehicle  of  infection  is  of  less  importance 
than  was  formerly  believed.  Very  little  evidence  has  been 
found  in  support  of  the  theory  and  much  against  it.  It  has 
been  definitely  proved  that  some  diseases  are  not  air-borne 
and  the  evidence  against  certain  others  is  very  strong. 
While  the  tendency  is  thus  away  from  air  infection  we  must 

1  Kitasato,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Pub.  Health 
Rep.,  1911,  XXVI,  567. 

»  Strong,  J.  Am.  M.  Ass.,  Chicago,  1911,  LVII,  1270. 


282       THE  SOURCES  AND  MODES  OF  INFECTION 

be  on  our  guard  lest  our  generalization  carry  us  too  far. 
It  may  be  a  fact  that  most  diseases  are  not  air-borne, 
and  yet  further  investigation  may  show  that  certain  other 
diseases  concerning  which  we  are  still  in  doubt  may  be 
usually  transmitted  in  this  way. 

Winslow  has  recently  been  making  some  interesting  ex- 
periments in  New  York  concerning  the  presence  of  living 
streptococci  in  dust.  He  finds  that  certain  types  of  strep- 
tococci characteristic  of  human  secretions  are  found  in  a 
viable  condition  in  enormous  numbers  in  both  house  and 
street  dust,  notwithstanding  the  fact,  which  also  has  been 
demonstrated,  that  these  bacteria  tend  to  die  off  with  great 
rapidity  when  thrown  off  from  the  body.  Several  observers 
in  different  parts  of  the  country  have  recently  noted  the 
presence  of  streptococci  in  outbreaks  of  severe  sore  throat, 
and  Winslow  asks  whether  it  may  not  be  possible  that  street 
dust  as  well  as  indoor  dust  may  be  a  factor  in  the  spread  of 
this  affection. 

Infection  by  Air  at  Short  Range.  —  Most  of  the  discussion 
thus  far  has  related  in  large  part  to  alleged  extension  of  dis- 
ease through  the  air  from  apartment  to  apartment,  or  from 
house  to  house,  or  from  hospital  to  adjoining  districts. 
Transmission  over  such  considerable  distances  might  be 
rare  or  even  impossible,  and  yet  nevertheless  the  air  might 
be  the  chief  vehicle  in  ordinary  institution  or  family  infec- 
tion. That  it  is  believed  to  be  so  is  indicated  by  the  com- 
mon regulation  that  a  wet  sheet  shall  be  hung  before  the 
door  of  the  sick-room  to  prevent  the  escape  of  germs,  by  the 
wearing  of  caps  by  visitors  and  the  disinfection  of  inacces- 
sible portions  of  the  room.  If  we  ask  the  reason  for  this 
universal  belief  in  the  importance  of  air-borne  infection,  we 
shall  find  that  it  is  based  entirely  on  theory,  and  that  there 
is  no  clinical  evidence  at  all  to  indicate  that  such  a  mode  of 
infection  is  of  any  great  importance.  What  evidence  we 
have  indicates  rather  that  infection  by  means  of  the  air  is 
of  comparatively  little  importance. 


INFECTION  BY  AIR  283 

Reasons  for  Belief.  —  The  real  reasons  why  people  gener- 
ally attach  so  much  importance  to  this  mode  of  infection  are, 
first,  the  hearty  belief  in  the  general  theory  of  aerial  infection 
which  has  prevailed  from  remote  antiquity,  and,  secondly, 
because  infection  so  often  takes  place  Avhen  there  has  not  been 
any  known  contact.  Contact  is  the  most  certain  and  obvious 
mode  of  infection,  and  other  modes  should  not  be  assumed 
without  good  reason.  The  burden  of  proof  rests  on  those 
who  make  the  assumption. 

Air  and  Aseptic  Surgery.  —  The  historj^  of  aseptic  surgery 
is  very  suggestive  in  connection  with  the  theory  of  air-borne 
infection.  Lister  at  first  unquestionably  considered  the  air 
to  be  the  chief  source  of  wound  infection,  and  this  view  for 
awhile  dominated  surgical  practice.  Then  gradually  more 
and  more  attention  was  given  to  contact  infection,  contact 
with  instruments,  contact  with  the  patient's  own  skin,  con- 
tact with  the  operator's  hands.  As  danger  from  these  sources 
was  more  and  more  perfectly  guarded  against,  surgery  became 
more  and  more  successful  and  aerial  infection  was  less  and 
less  dreaded.  A  successful  surgeon  of  my  acquaintance  tells 
me  that  he  can  operate  with  as  little  wound  infection  in  a 
tenement  house  as  in  the  best  operating  room.  Ochsner^ 
says,  "Air  infection  is  not  impossible,  but  practically  no  wound 
infection  is  to  be  considered  except  from  contact."  Most 
surgeons  at  the  present  time  consider  aerial  infection  of  very 
little  importance.  Nevertheless  it  has  been  shown,  as  we 
shall  see,  that  the  air,  even  of  well-constructed  operating 
rooms,  contains  considerable  numbers  of  living  pus-forming 
bacteria.  Yet  they  are  usually  not  numerous  enough  nor 
virulent  enough  to  infect,  and  unless  there  is  some  other 
source  of  infection  the  wound  heals  aseptically.  Pus-forming 
bacteria  are  quite  resistant,  and  are  by  far  the  most  numerous 
and  ubiquitous  of  all  disease  germs  and  more  likely  to  be 
found  in  the  air,  and  the  fact  that  they  generally  fail  to  infect 
should  give  pause  to  any  claim  that  the  much  less  numer- 
1  Ochsner,  Clinical  Surgery,  Chicago,  1902,  26. 


284        THE  SOURCES  AND  MODES  OF  INFECTION 

ous  air-borne  germs  of  other  diseases  are  the  chief  source 
of  infection. 

Sewer  Air  and  Bacteria.  —  In  this  connection  the  relation 
of  sewer  air  to  the  transport  of  bacteria  should  be  referred  to. 
Winslow  ^  in  a  very  valuable  paper  gives  a  brief  history  of 
the  theories  on  this  subject,  and  shows  how  the  former  ideas 
as  to  the  great  danger  to  be  apprehended  from  sewer  air 
gradually  gave  way  before  increasing  knowledge  of  bacteria, 
and  particularly  after  it  was  determined  that  these  organisms 
are  not  readily  detached  from  moist  surfaces.  From  that 
time  it  was  generally  believed  that  sewer  air  had  little  or 
nothing  to  do  with  the  extension  of  the  infectious  diseases. 
The  subject,  however,  was  reopened  by  Andre wes  '  and  Hor- 
rocks.^  The  latter  showed  that  under  natural  conditions 
B.  prodigiosus  and  also  the  bacillus  of  typhoid  fever  might 
be  carried  by  the  sewer  air  long  distances  and  escape  at  man- 
hole and  soil-pipe  openings.  Lewis  ^  also  showed  that  sewage 
bacteria  could  be  found  in  the  air  passing  over  a  sewage  farm, 
and  also  in  that  blowing  at  low  tide  over  a  beach  where 
sewage  was  discharged.  Winslow  by  a  series  of  careful  experi- 
ments confirmed  the  work  of  Horrocks,  but  went  further  and 
determined  the  number  of  bacteria  that  are  transported  in 
this  way.  He  found,  as  have  others,  that  mechanical  splash- 
ing may  produce  a  slight  local  infection  of  the  air  in  immediate 
contact  with  the  spray,  but  such  infection  extends  for  only 
a  very  short  distance  and  persists  for  not  more  than  a  minute 
or  two.  A  careful  quantitative  study  of  the  air  of  nineteen 
different  plumbing  systems  in  various  parts  of  Boston  showed 
that  very  few  sewage  bacteria  are  found  in  such  air.  These 
bacteria  were  found  only  four  times   in   200   liters  of  air, 

'  Winslow,  Rep.  to  Ran.  Com.  Nat.  Ass.  Master  Plumbers,  1907-09; 
Abst.  Am.  J.  Pub.  Ilyg.,  Bost.,  1909,  V,  640. 

2  Andrewes,  Rep.  Med.  Off.  Local  Gov.  Bd.,Lond.,  1906-07,  XXXVI, 
183,  and  1907-08,  XXXVII,  266. 

'  Horrocks,  Pub.  Health,  Lond.,  1907,  XIX,  495. 

*  Lewis,  Scot.  M.  &  S.  J.,  Edin.,  1907,  XX,  487. 


INFECTION  BY  AIR  285 

and  then  in  the  presence  of  mechanical  spraying  of  sewage 
at  the  point  of  collection.  To  illustrate  the  paucity  of  dan- 
gerous bacteria  in  sewer  air  he  says: 

"  In  a  surface  water  of  good  quality,  like  that  of  New 
York  City,  the  colon  bacillus  can  almost  invariably  be  iso- 
lated from  ten  cubic  centimeters.  This  means  a  slight  degree 
of  intestinal  pollution,  but  experience  has  shown  that  the 
chance  of  infection  from  such  a  water  is  but  slight;  and  we 
drink  it  without  serious  alarm.  If  one  were  to  breathe  for 
24  hours  the  undiluted  air  of  a  house-drainage  system,  at 
any  point  not  immediately  infected  by  mechanical  splashing, 
it  appears  that  less  than  fifty  intestinal  bacteria  would  be 
taken  in;  for  the  daily  .consumption  of  air  is  about  10,000 
liters,  and  in  200  liters  I  obtained  negative  results  from  air 
of  this  sort.  In  drinking  New  York  water  twice  as  many 
colon  bacilli  are  ingested  every  day,  for  1000  cubic  centi- 
meters is  a  small  amount  for  daily  consumption.  So  there 
would  be  less  danger  of  contracting  disease  from  continually 
breathing  the  air  of  a  vent  pipe,  or  of  a  soil  pipe,  except 
where  liquid  is  actually  splashing,  than  from  drinking  New 
York  water." 

Anthrax. —  Some  time  since,  while  considering  this  subject, 
it  occurred  to-  me  that  anthrax  ought  to  be  air-borne  more 
often  than  any  other  disease.  The  spores  are  extremel}^  resist- 
ant, and  are  found  in  great  numbers  in  hair,  wool,  etc.,  and 
the  manipulation  of  these  materials  is  quite  likely  to  raise  a 
considerable  amount  of  dust.  If  this  be  so,  and  if  floating 
germs  are  carried  to  the  alveoli  of  the  lungs,  as  is  alleged,  the 
pulmonary  type  of  this  disease  ought  to  be  very  common. 
Formerly  this  seems  to  have  been  the  case.  According  to  the 
report  of  the  Local  Government  Board, ^  of  thirty-two  cases 
occurring  in  the  woolen  industry  of  Bradford  during  nine 
months,  twenty-three  were  of  the  internal  type.  Since  then 
great  effort  has  been  made  to  eliminate  dust  as  much  as 
possible  from  the  woolen  and  other  industries  in  which  dry 
1  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1882-83,  XII,  98 


286         THE  SOURCES  AND  MODES  OF  INFECTION 

infected  material  is  handled.  As  a  consequence,  as  stated  in 
the  last  report  of  the  factory  inspector  which  I  have  at  hand/ 
of  four  hundred  forty-four  cases  of  industrial  anthrax  in  Eng- 
land from  1899  to  1907  only  twenty-one  were  of  the  pul- 
monary type,  and  all  of  these  twenty-one  were  in  the  dusty 
woolen  industry.  The  disease  is  not  nearly  so  common  in 
the  United  States,  owing  to  the  fact  that  less  infected  material 
is  imported,  but  of  fifteen  cases  in  Philadelphia  two  only  were 
internal.  Even  now,  under  the  best  conditions,  there  must 
be  considerable  infected  dust  caused  b}^  opening  and  separat- 
ing the  bales,  and  the  comparative  rarity  of  the  pulmonary 
type  of  the  disease  indicates  that  it  is  not  very  easily  air- 
borne, though  it  appears  almost  certain  that  some  cases 
develop  in  this  manner.  Furthermore,  it  appears  that  this 
disease  may  be  transmitted  by  the  air  even  out  of  doors. 
Legge  states  that  he  has  seen  two  horses  infected  by  feeding 
where  the  dust  from  the  blower  of  a  wool-sorting  room  was 
discharged,  and  Silberschmidt  ^  reported  a  similar  infection  of 
eight  out  of  twenty-two  horses  near  a  hair  factory  at  Zurich. 
Slight  Evidence  that  Disease  is  Air-borne.  —  It  is  thus 
seen  that  clinical  and  epidemiological  evidence  of  the  spread 
of  contagious  diseases  through  the  medium  of  the  air  is 
scanty.  No  proof  of  extension  through  the  external  air  is 
presented  for  any  important  disease  except  smallpox,  and 
this  is  far  from  conclusive.  I  have  never  seen  any  good  clin- 
ical evidence  that  diseases  are  air-borne,  even  indoors.  On 
the  contrary,  there  is  much  evidence  that  this  mode  of  infec- 
tion is  not  a  common  one.  The  reasons  for  the  widespread 
belief  in  the  transmission  of  disease  through  the  air  seem  to 
be  entirely  theoretical,  and  to  have  been  developed  simply 
because  no  other  satisfactory  explanation  was  at  hand.  Let 
us  now  consider  laboratory  and  experimental  evidence. 

'  Report  Chief  Inspector  of  Factories  and  Workshops,  1904,  49; 
1905,  49;  1906,  38;  1907,  .56;  also  LeRRe,  Lancet,  Lond.,  1905,  I,  841. 

"  Silberschmidt,  Ztschr.  f.  llyg.  u.  Infcctionskrankh.,  Leipz.,  1896, 
XXI,  455. 


INFECTION  BY  AIR  287 

Bacteria  not  given  off  from  Moist  Surfaces.  —  Among 
the  many  new  conceptions  which  resulted  from  the  study  of 
bacteriology,  one  of  the  most  novel  was  that,  contrary  to  all 
previous  ideas,  bacteria  are  not  given  off  from  and  are  not 
readily  detached  from  moist  surfaces  or  liquids  in  a  state  of 
rest.  This  was  first  shown  by  Nageli^  and  has  been  amply 
confirmed  by  Buchner,^  Wernich,^  Hubs*  and  others. 

When  this  became  known,  numerous  experiments  were 
undertaken  to  determine  whether  the  expired  air  was  free 
from  germs,  as  in  accordance  with  the  newly  discovered  facts 
it  should  be.  Tyndall  was  the  first  to  show  that  bacteria 
are  not  found  in  expired  air,  and  Gotschlich  ^  cites  a  dozen 
or  so  workers,  all  of  whom  obtained  only  negative  results 
from  an  examination  of  the  expired  air.  According  to  Fliigge," 
Cadeac  and  Malet,  Grancher  and  Gennes,  and  Miiller  were 
unable  to  find  tubercle  bacilli  in  the  ordinary  expiration  of 
phthisical  patients,  and  these  early  observations  have  been 
amply  confirmed  by  others. 

It  has  been  shown  not  only  that  air  currents  are  incapable 
of  removing  bacteria  from  liquids  but  also  that  such  currents 
do  not  remove  them  from  the  surfaces  of  solids.  Most  mate- 
rials which  contain  pathogenic  bacteria,  such  as  culture  media, 
saliva,  mucus,  pus,  excreta,  etc.,  present,  when  dry,  a  some- 
what hard  and  often  glazed  surface,  so  that  it  is  not  sur- 
prising that  exceedingly  strong  air  currents,  even  of  sixty 
meters  per  second,  do  not  remove  the  contained  germs.     This, 

1  Nageli,  Die  niederen  Pilze,  Miinchen,  1877,  107,  Untersuchugen  in 
die  niederen  Pilze,  1882. 

^  Nageli  u.  Buchner,  Sitzungsber.  d.  Bay.  Akad.  d.  Wiss.,  Miinchen, 
7  June,  1879 . 

'  Wernich,  Virchow's  Arch.  f.  path.  Anat.  [etc.],  Berl.,  1880,  LXXIX, 
424. 

*■  Huhs,  Ztschr.  f.  Tuberk.  u.  Heilstattenw.,  Leipz.,  1906,  IX,  396. 

^  Gotschlich,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1902,  I, 
171. 

^  Fliigge,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
107. 


288         THE  SOURCES  AND  MODES  OF  INFECTION 

according  to  Gotschlich/  has  been  demonstrated  by  Nageli, 
Buchner,  Wernich,  Hamburger  and  Stern,  and  Fliigge.  Got- 
schlieh  says  that  Honssell  found  it  impossible  to  detach 
bacteria  from  infected  clothing. 

Infection  in  Dust.  —  So  firmly  was  the  theory  of  aerial 
infection  intrenched  in  the  minds  of  men,  that  search  was 
made  for  some  other  means  than  the  expired  breath  by 
which  bacteria  might  get  into  the  air.  It  was  very  early 
found  that  many  bacteria  could  withstand  drying  for  con- 
siderable periods  of  time,  and  it  was  at  once  suggested  that 
material  containing  disease  germs  might  become  dry  and  pul- 
verized, and  that  the  resulting  infective  dust  might  readily 
be  transported  by  currents  of  air.  Indeed  Koch^  was  one 
of  the  earliest,  as  well  as  one  of  the  strongest,  supporters  of 
this  view. 

Resistance  of  Bacteria  to  Drying.  —  If  dust  is  a  vehicle 
for  the  transport  of  the  germs  of  disease,  and  bacteria  are 
air-borne  on  or  in  bits  of  dust,  or  float  as  separate  particles, 
they  must  withstand  a  considerable  amount  of  drying.  That 
some  species  do  retain  their  vitality  and  virulence  after 
becoming  quite  thoroughly  dry,  has  been  demonstrated.  Sys- 
tematic studies  of  the  effects  of  drying  and  of  light  on  dif- 
ferent disease-producing  bacteria  have  been  made,  and  almost 
every  germ  has  been  examined  from  this  standpoint  by  men 
particularly  interested  in  working  out  its  biological  characters. 
In  some  instances,  as,  for  example,  the  tubercle  bacillus,  the 
experiments  and  observations  are  very  numerous.  In  the 
chapter  on  fomites  infection,  the  resistance  of  the  different 
pathogenic  organisms  to  dryness  and  to  light  was  considered. 
While  some  species  were  shown  to  have  very  little  resisting 
power,  the  germs  surviving  for  a  few  hours  or  a  few  minutes 
only,  others,  like  the  bacilli  of  typhoid  fever,  diphtheria  and 

^  Gotschlich,  Kollc  u.  Wassormann,  Ilandbuch  [etc.],  Jena,  1902,  I, 
170. 

*  Koch,  Mit.  a.  d.  k.  Gesundheitsamtc,  1884,  II,  Trans.  Sydenham 
Soc.  Pub.,  CXX. 


INFECTION  BY  AIR  289 

tuberculosis,  maj^,  when  dry,  retain  their  vitaHty  for  months. 
In  addition  to  the  general  knowledge  of  the  resisting  power  of 
bacteria,  which  has  been  accumulating,  special  and  systematic 
.attempts  have  been  made  to  determine  directly  the  chances 
of  infection  by  air-borne  dust. 

Studies  on  the  Drying  of  Germs.  —  Among  the  earliest 
work  of  this  kind  was  that  by  Germano.^  He  employed  room 
dust  and  different  kinds  of  earth,  which  after  sterilization 
were  inoculated  with  cultures  of  bacteria  grown  in  various 
media.  He  found  that  generally  the  bacteria  perished  sooner 
in  room  dust  than  in  other  materials,  and  that  bacteria 
which,  like  the  typhoid  bacillus,  might  survive  for  months 
even  when  dried  on  clothing  or  solid  material,  would  speedily 
die  in  a  very  short  time  in  dust.  After  a  large  number  of 
experiments  he  concluded  that  cholera,  plague,  typhoid  fever, 
influenza  and  gonorrhea  could  not  be  dust-borne;  that  under 
certain  circumstances,  with  strong  air  currents,  streptococcus 
and  the  germs  of  pneumonia  and  of  diphtheria  might  be  air- 
borne, and  that,  besides  the  spores  of  anthrax  and  tetanus, 
many  of  the  pus  organisms,  meningococcus  and  the  tubercle 
bacillus,  might  be  transported  in  dust.  It  is  suspected  that 
he  did  not  emplo}^  the  true  coccus  of  cerebro-spinal  meningi- 
tis, for  recent  workers  are  agreed  that  this  bacterium  has  very 
weak  powers  of  resistance.  His  results  with  the  pneumo- 
coccus  also  are  surprising,  as  this  too  is  rather  feeble. 

Neisser^  in  1898  made  a  careful  study  of  the  strength  of 
air  currents  necessary  to  move  dust  infected  with  various 
pathogenic  bacteria.  He  showed  that  currents  of  from  1 
to  4  mm.  per  second  are  sufficient  to  transport  room  dust, 
and  it  was  chiefly  with  such  currents  that  he  worked.  He 
used  from  twenty  to  thirty  drops  of  an  agar  culture  mixed 
with  30  c.c.  of  sterile  dust.  He  drew  dust  through  narrow 
tubes  in  a  rather  complicated  apparatus,  and  it  appears  that 

1  Germano,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1897, 
XXIV,  403;  1897,  XXV,  439;  1897,  XXVI,  66,  273. 

*  Neisser,  Ueber  Lauftstaub-Infection,  Inaug.  Dis.,  Breslau,  1898. 


290         THE  SOURCES  AND  MODES  OF  INFECTION 

the  conditions  were  too  far  removed  from  the  natural  to 
render  the  results  of  much  value.  Neisser's  conclusions  were 
that  diphtheria,  typhoid  fever,  plague,  cholera,  pneumonia, 
are  not  dust-borne  diseases,  but  that  spores,  most  of  the  pus 
organisms,  tubercle  bacilli,  and  the  germs  of  cerebro-spinal 
meningitis  may  be  so  carried.  It  will  be  seen  that  to  a  large 
extent  he  agrees  with  Germano,  but  it  is  to  be  noted,  however, 
that  his  tests,  like  those  of  Germano,  were  all  culture  tests, 
except  those  for  tuberculosis,  in  which  alone  animal  inocula- 
tions were  made.  Besides  such  systematic  work  as  that  of 
Germano  and  Neisser,  much  has  been  done  in  the  study  of 
special  diseases  by  men  particularly  interested  therein. 

Drying  of  Typhoid  Bacilli.  —  Firth  and  Horrocks  ^  found 
that  the  tyi^hoid  bacillus  would  live  for  23  days  in  sand  dry 
enough  to  be  blown  by  the  wind.  Harrison  and  Harrison,^ 
working  in  India,  recovered  the  organism  after  118  hours 
when  kept  in  diffused  light  in  very  dry  dust.  Aldridge^ 
moistened  sand  with  urine  containing  typhoid  bacilli  on 
three  successive  days,  and  dried  it  on  the  fourth  day,  and 
blew  it  with  a  bellows  over  sterile  bouillon.  He  recovered 
the  bacillus  on  the  1st,  4th  and  9th  day  thereafter. 

Horrocks  ^  showed  that  the  micrococcus  of  Mediterranean 
fever  would  survive  in  dry  soil  for  about  3  weeks. 

Drying  of  Diphtheria  Bacilli.  —  Fliigge  ^  says  that  diph- 
theria bacilli  p(!rish  when  dry  enough  to  be  blown  about  in 
dust.  This  is  confirmed  by  Pernice  and  Scagliosi  and  Reyes.** 
Reyes  found  th(\v  would  live  for  14  days  in  dry  sand. 

Drying  of  Plague  Bacilli.  —  Tidswell,^  experimenting  with 
dust  of  various  kinds,  could  not  recover  the  bacillus  of  bu- 

»  Firth  and  Horrocks,  Brit.  M.  J.,  Lond.,  1902,  II,  936,  1094. 
^  Harrison  and  Harrison,  J.  Roy.  Army  Med.  Corps,  Lond.,  1904, 
II,  721. 

»  AldridKo,  Indian  M.  C.az.,  C^alcutta,  1903,  XXXVIII,  249. 

*  Horrocks,  J.  Roy.  Army  Mod.  Corps,  Lond.,  1905,  V,  78. 

"  FliJK^c,  Ztsdir.  f.  Hyt^.  u.  Iiifcctionskrankli.,  Lcii)z.,  1895,  XVII,  401. 

•  Cited  l)y  ( Jcrmano. 

'  Tidswcll,  l{('i).  oM  I'lat^iic  in  (^uccnslami,  1902,  (37. 


INFECTION  BY  AIR  291 

borne  plague  after  11  days  when  the  dust  was  dried  under 
natural  conditions,  and  it  usually  died  within  3  or  4  days. 
When  dried  very  slowly  it  lived  about  twice  as  long.  Rose- 
nau^  found  that  this  bacillus  did  not  live  in  dried  bone  dust 
over  6  days,  and  he  did  not  recover  it  from  dry  and  sterile 
garden  soil  after  1  day. 

Drying  of  Tubercle  Bacilli.  —  More  attention  has  been 
given  to  the  tubercle  bacillus  than  to  any  other  pathogenic 
organism.  Besides  other  experiments  referred  to  elsewhere 
in  these  pages  it  may  be  mentioned  that  Kirstein  ^  experi- 
mented with  various  kinds  of  dust,  and  could  not  find  living 
tubercle  bacilli  after  8  days.  The  dust  was  artificially 
infected  and  exposed  to  diffused  light.  He  thinks  droplet  in- 
fection far  rnore  important  than  dust  infection.  Cadeac  ^ 
was  unable  to  reduce  sputum  to  dust  until  it  had  been  dried 
10  to  12  days,  while  the  tubercle  bacilli  had  nearly  died  out 
on  the  6th  day.  Even  when  pulverized  sputum  is  injected 
into  animals,  tuberculosis  rarely  develops,  and  it  must  be 
still  rarer  as  the  result  of  inhalation.  Sticher  *  also  and 
Beninde  ^  found  it  difficult  to  demonstrate  living  bacilli 
in  dried  and  pulverized  sputum  under  natural  conditions. 
Nevertheless  most  observers  do  find  living  tubercle  bacilli  in 
dust,  though  usually  with  weakened  virulence. 

Drying  of  Cholera  Spirilla.  —  According  to  Germano,  chol- 
era spirilla  may  sometimes  survive  in  dust  for  3  days,  but 
oftentimes  they  die  in  1  day.  He  says  that  Honssell  was 
never  able  to  obtain  living  spirilla  from  infected  dust, 
though  Uffelmann  was  able  to  do  so  for  a  short  period. 

'  Rosenau,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 
No.  4,  1901. 

^  Kirstein,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1905,  L,  186. 

'  Cadeac,  Lyon  Med.,  1905,  CV,  893;  also  Lyon  Med.,  1908,  CXI, 
532. 

*  Sticher,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
163. 

^  Beninde,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
193. 


292         THE  SOURCES  AND  MODES  OF  INFECTION 

William^    believes    that    cholera    cannot    be    a   dust-borne 
disease. 

Tubercle  Bacilli  in  Dust.  —  Of  more  practical  importance 
than  experiments  with  artificially  infected  dust  is  the  deter- 
mination of  the  presence  or  absence  of  disease-producing 
bacteria  in  supposedly  infected  localities.  The  chief  interest 
in  such  investigations  has  centered  in  tuberculosis.  Cornet  ^ 
has  made  a  more  extensive  study  than  any  one  else  of  the 
natural  distribution  of  tubercle  bacilli  in  dust.  He  examined 
147  specimens  of  dust  collected  from  hospital  wards,  dis- 
pensaries, private  houses,  streets,  etc.  No  bacilli  were  found 
in  the  street  or  in  places  not  occupied  by  the  tuberculous, 
and  even  in  the  environment  of  the  consumptive  germs  were 
found  only  when  the  patient  was  careless  in  the  disposal  of 
sputum.  Cornet's  observations  have  been  confirmed  by  Rem- 
bold,  Kriiger,  Kastner,  Ballinger,  Kusterman,  Le  Noir  and 
Camus  and  Enderlin,  besides  others  elsewhere  referred  to. 
Gotschlich  ^  examined  one  hundred  and  nineteen  specimens 
of  dust  from  streets  and  public  places  and  was  not  able  to 
demonstrate  the  presence  of  tubercle  bacilli.  While  most 
observers  have  been  unable  to  find  the  tubercle  bacillus  in 
street  dust,  it  is  said  to  have  been  found  by  Manfredi  *  and 
Schnirer.^  Prausnitz  *^  and  Petri  ^  obtained  tubercle  bacilli 
from  the  dust  in  railway  carriages,  and  Bissell  ^  found  them 
in  tram  cars  in  Buffalo. 

'  William,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Lcipz.,  1893,  XV,  1G6. 

^  Cornet,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1885,  V,  98; 
Nothnagel's  Encyclopedia  of  Pract.  Med.,  Phila.  &  Lond.,  1907,  Tuber- 
culosis, 8.5. 

'  Gotschlich,  Die  Verhrcitung  dor  Tuberkelbacillon  in  Staub  von 
Raumon  niit  starkcni  Menschenverkchr,  Inaug.  Dis.,  IJreslau,  1903. 

*  Manfredi,  Jahrcsb.  u.  d.  Fortschr.  .  .  .  d.  i)at  h.  Mik.,  Baumgarten, 
1891,  VII,  ruO. 

6  Schnirer,  Wien.  med.  Prcsse,  1891,  XXXII,  3. 

8  Prausnitz,  Arch.  f.  Hyg.,  Miincihen  u.  Loipz.,  1891,  XII,  192. 

'  Petri,  Arb.  a.  d.  k.  Oesund.-Amt.,  Rerl.,  1894,  IX,  76. 

«  Bissell,  N.  York  M.  J.,  1895,  LXII,  783. 


INFECTION  BY  AIR  293 

Some  observers  have  not  found  the  bacilli  so  numerous  as 
did  Cornet.  Thus  Hill/  following  Cornet's  methods,  obtained 
virulent  bacilli  in  but  5  of  496  swabbings  from  private 
Jiouses  where  there  were  cases  of  the  disease,  and  in  3  of 
180  swabbings  from  hospital  wards. 

Heymann  ^  has  criticised  Cornet's  findings  on  the  ground 
that  the  latter  recovered  the  dust  by  means  of  moist  swabs, 
thereby  perhaps  taking  up  many  bacilli  which  were  attached 
to  the  floor,  table,  etc.,  and  which  would  not  therefore  have 
any  part  in  air-borne  infection.  He  does  not  find  living 
bacilli  so  numerous  in  dust  as  did  Cornet.  Heymann  in  120 
tests  found  them  only  one-third  as  often,  but  Coats,^  follow- 
ing Heymann's  methods,  was  able  by  inoculation  tests  to 
demonstrate  the  presence  of  tubercle  bacilli  in  66  per  cent  of 
specimens  of  dust  obtained  from  fourteen  rooms  occupied  by 
tuberculous  patients.  On  the  whole,  it  appears  that  virulent 
tubercle  bacilli  are  quite  commonly  found  in  the  dust  of 
rooms  occupied  by  careless  tuberculous  patients. 

In  this  connection  may  be  mentioned  an  experiment  of 
Heymann's  in  which  he  rubbed  and  shook  a  sputum-infected 
handkerchief,  after  two  days'  drying,  in  a  closed  box,  and 
found  floating  bacilli  after  the  lapse  of  an  hour. 

Meningococcus  in  Dust.  —  Jaeger*  claimed  to  have  found 
the  meningococcus  on  the  floor  of  barracks,  and  Netter^  the 
pneumococcus  in  the  dust  of  a  sick-room  four  weeks  after  the 
case  was  removed,  but  from  w'hat  is  now  known  of  the  resist- 
ance of  these  bacteria  this  is  highly  improbable.  Wash- 
bourn  and  Eyre^  found  the  pneumococcus  in  dust  from  a 
ward  and  laboratory  at  Guy's  Hospital,  but  failed  to  find  it  in 

1  Hill,  Am.  Pub.  Health  Ass.  Rep.,  1902,  XXVIII,  209. 

2  Heymann,  Ztschr.  f.  Hyg.  u.  Infeetionskrankh.,  Leipz.,  1901, 
XXXVIII,  21. 

^  Coats,  Trans.  Brit.  Cong,  on  Tuberculosis,  1901,  I,  p.  88. 
*  Jaeger,  Deutsche  med.  Wchnschr.,  1899,  XXV,  472. 
'  Netter,  Compt.  rend.  Soc.  de  biol.,  Par.,  1897,  IV,  538. 
'  Washbourn  and  Eyre,  Lancet,  Lond.,  1902,  II,  1440. 


294       THE  SOURCES  AND  MODES  OF  INFECTION 

street  dust.  Washbourn  says  that  it  has  also  been  found  in 
dust  by  Emmerich,  Maximowitch  and  Netter. 

Diphtheria  Bacilli  in  Dust.  ■ —  These  bacilli  have  been  found 
in  the  dust  of  a  scarlet-fever  ward,'  and  are  said  to  have  been 
found  in  a  diphtheria  ward  by  Richardiere  and  Tallemer,^ 
but  Schlichter  ^  could  not  find  them  in  a  hospital  in  Vienna. 
Cobbett  *  exposed  plates  in  a  diphtheria  ward,  but  could 
obtain  no  bacilli  except  when  the  plates  had  been  touched 
by  the  fingers  of  the  patients. 

Dust  and  Other  Diseases.  —  There  has  been  much  dis- 
cussion of  late  in  England  about  the  necessity  for  disinfecting 
schoolrooms,  and  examination  of  school  dust  has  shown  the 
presence  of  colon  bacilli  ^  and  the  pus  organisms." 

General  Conclusions.  —  While  these  facts  relating  to  the 
resistance  of  disease  germs  to  drying,  and  their  presence  in 
supposedly  infected  localities,  afford  no  definite  information 
as  to  the  danger  to  be  apprehended  from  infection  by  air- 
borne dust,  they  do  lead  to  some  tentative  conclusions.  It 
is  scarcely  possible  that  gonorrhea,  influenza,  cerebro-spinal 
meningitis  and  pneumonia  can  be  dust-borne.  It  is  possible, 
perhaps,  but  highly  improbable,  that  plague  and  cholera  can 
be  so  borne.  The  bacteriological  evidence  indicates  that  the 
germ  of  typhoid  fever,  dysentery,  Mediterranean  fever,  diph- 
theria, tuberculosis  and  suppuration  may  be  carried  by  float- 
ing dust,  and  it  is  certainly  possible  for  anthrax  and  other 
spores. 

Danger  from  Dust  Slight. — Bacteriology  also  teaches  what 
is  often  forgotten,  that  pathogenic  bacteria,  with  the  ex- 
ception of  spores,  die  off  quite  rapidly  when  dried,  and  that 
the  survivors  usually  have  a  weakened  virulence.     If  in  a 

>  Rennoy,  Puh.  Ilcjilth,  Lond.,  lOO.'J,  XVII,  706. 

2  lliclianliorc  ct  Talloinor,  Gaz.  d.  nial.  enfant  [etc.],  Par.,  1899,  X. 

»  Schlichter,  Arch.  f.  Kinderh.,  Stuttg.,  1892,  XIV,  129. 

«  Cobbett,  J.  Royal  San.  Inst.,  Lond.,  1904,  XXV,  405. 

*  Hewlett,  Lancet,  Lond.,  1909,  I,  741,  815,  889. 

•  Kerr,  Med.  Off.  Educa.,  Lond.,  1908,  31. 


INFECTION  BY  AIR  295 

sick-room  or  hospital  ward  the  germs  of  disease  are  scattered 
so  freely  on  the  floor  or  room  contents  that  enough  of  them 
can  survive  drying  and  pulverization  to  float  in  the  air  and 
cause  disease,  the  opportunities  for  contact  infection  with  the 
comparatively  fresh  infective  material  must  be  very  great,  so 
great,  it  seems  to  me,  that  infection  by  air  under  such  condi- 
tions must  be  very  insignificant  or  entirely  negligible  as  com- 
pared with  infection  by  contact. 

Droplet  Infection.  —  Another  way  in  which  living  bacteria 
may  be  carried  by  the  air  is  in  tiny  floating  particles  of  liquid. 
Fliigge^  was  the  first  to  call  attention  to  the  fact  that  during 
speaking,  and  especially  during  loud  talking,  coughing  and 
sneezing,  tiny  droplets  of  saliva  are  thrown  off  from  the 
mouth.  Indeed  such  droplets  may  be  readily  seen  in  the 
proper  light,  and  it  hardly  needed  special  experiment  to  prove 
their  existence.  Nevertheless,  Flligge^  and  Laschtschenko,' 
by  infecting  the  mouth  with  B.  prodigiosus,  showed  that 
germ-carrying  droplets  are,  during  coughing,  borne  to  a  dis- 
tance of  nine  meters  in  front  of  the  mouth.  These  droplet 
experiments  have  been  repeated  with  confirmatory  results  by 
Goldie,  Esmarch,  B.  Frankel,  Moller,  Hiibner,  Weismayr  and 
Koniger,  and  the  last  mentioned  has  shown  that  the  droplets 
may  be  found  two  meters  behind  the  person  coughing.* 
Goldie  showed  that  in  fourteen  per  cent  of  the  cases  tubercle 
bacilli  could  be  caught  on  plates  after  a  single  act  of  coughing. 
Every  patient  examined  at  one  time  or  another  gave  positive 
results.  No  bacilli  were  found,  even  as  near  as  six  inches, 
during  deep  breathing,  but  after  coughing  they  could  be 
recovered  from  all  parts  of  the  room. 

^  Fliigge,  Ztschr.  f.  Hyg.  u.  Infectiouskrankh.,  Leipz.,  1897,  XXV, 
179. 

2  FIugge,Ztsch.f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX,  107. 

'  Laschtschenko,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899, 
XXX,  125. 

*  Koniger,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1900,  XXXIV, 
119. 


296        THE  SOURCES  AND  MODES  OF  INFECTION 

Amount  of  Droplet  Infection.  —  Since  it  has  been  shown  by 
Fliigge  that  droplets  from  speaking  may  float  for  from  five 
to  six  hours,  and  be  transported  by  air  currents  of  only  one 
mm.  per  second,  it  is  not  surprising  that  they  should  be  car- 
ried such  distances.  Nor  is  it  surprising  that  Hutchinson^ 
was  able  to  prove  that  a  fine  spray  of  a  culture  of  B.  pro- 
digiosus  was  carried  fifty-five  meters  along  a  corridor,  and  up 
two  flights  of  stairs,  and  also  a  considerable  distance  out  of 
doors.  Others  have  shown  that  the  bacteria  of  the  mouth 
may  be  carried  by  the  air  during  speaking  over  a  large  room 
or  hall.^  Leon^  showed  that  in  speaking  three  hundred 
words  250,000  bacteria  were  thrown  off  from  the  mouth,  and 
Ziesche^  found  over  20,000  tubercle  bacilli  on  a  plate  324 
sq.  cm.  exposed  for  half  an  hour.  But  it  has  further  been 
shown  by  Kirstein^  and  Koniger*'  and  Laschtschenko'  that 
the  size  of  the  droplets  and  the  distance  they  can  be  carried 
depend  to  a  large  extent  upon  whether  the  liquid  is  thin  and 
watery  or  a  thick  mucus.  Hence  we  should  expect  that 
droplets  of  thick  sputum  would  not  be  carried  nearly  so 
far  as  droplets  of  more  liquid  saliva,  and  according  to 
Goldie^  droplets  of  the  saliva  rarely  carry  bacilli  but  only  the 
droplets  of  sputum. 

Quantitative  Experiments. — Since  the  above  was  written 
Winslow  and  Robinson^  have  published  a  very  interesting 

*  Hutchinson,  Ztschr.  f.  Hyg.  ii.  Infcctionskrankh.,  Leipz.,  1901, 
XXXVI,  223. 

2  Gordon,  Rop.  Med.  Off.  Loc:il  CJov.  Bd.,  I.ond.,  1902-03,  XXXII, 
421. 

3  Loon,  Arch.  f.  klni.  Cliir.,  Hcrl.,  1903-04,  LXXII,  904. 

*  Ziesche,  Ztschr.  f.  llyfr.  u.  Infcctionskrankh,  I.eipz.,  1907,  XLVII,  50. 
^  Krstein,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Lcipz.,  1900,  XXXV, 

123. 

"  Konigor,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1900,  XXXIV, 
119. 

'  Laschtschenko,  Ztschr.  f.  Hyg.  u.  Infectionskr.inkli.,  Leipz.,  1899, 
XXX,  125. 

"  Goldie,  (Canadian  Pract.  it  Rev.,  Toronto,  1899,  XXIV,  433. 

'  Winslow  and  Jioliinson,  Jour.  Infect.  Dis.,  Chicago,  1910,  VII,  17. 


INFECTION  BY  AIR  297 

paper  on  this  subject  giving  an  excellent  resume  of  previous 
investigations.  They  repeat  the  experiments  of  some  of  the 
European  writers,  and  like  them  they  find  that  if  the  mouth 
of  a  speaker  is  infected  with  a  specific  germ,  as  B.  prodigiosus, 
agar  plates  exposed  in  different  parts  of  the  room  show  nu- 
merous colonies  of  the  bacillus.  They  also,  by  the  exposure 
of  plates  in  the  room  with  the  speaker,  recovered  Gordon's 
Streptococcus  salivarius,  which  is  a  normal  inhabitant  of  the 
mouth.  The  authors  emphasize  the  distinction  noted  by 
others  between  the  larger  droplets  of  mouth  spray  which  con- 
tain the  most  bacteria  and  which  settle  out  of  the  air  in  the 
space  of  a  few  feet  from  the  mouth  and  the  smaller  droplets 
which  float  for  a  longer  time  and  may  pass  to  some  distance 
from  the  speaker,  and  which  alone  may  be  considered  as  prop- 
erly constituting  an  infection  of  the  air.  The  chief  interest 
in  their  studies  attaches  to  their  quantitative  work  carried 
out  on  the  lines  devised  by  Winslow  for  his  investigations  of 
sewer  air.  Out  of  140  liters  of  air  taken  at  various  points  in 
the  room  immediately  after  10  to  50  minutes'  loud  speaking 
by  a  person  whose  mouth  was  infected  with  B.  prodigiosus, 
the  bacillus  was  found  seven  times.  Of  74  liters  examined  for 
Streptococcus  salivarius  none  were  found  to  contain  this  nor- 
mal inhabitant  of  the  mouth.  The  authors  consider  that  an 
artificial  infection  of  the  mouth  may  give  too  high  an  index 
of  air  contamination,  while  the  normal  germs  of  the  mouth 
may  be  thrown  off  in  smaller  numbers  than  are  the  disease 
germs  from  sick  persons.  The  authors  conclude  that  these 
experiments  furnish  "no  basis  for  a  belief  that  tuberculosis 
or  any  other  disease  is  contracted  to  an  appreciable  extent 
through  the  inspired  air  "  and  are  "  in  harmony  with  the 
conviction  now  generally  gaining  ground  that  aerial  infection 
of  any  sort  is  a  minor  factor  in  the  spread  of  zymotic  disease." 
Lepra  Bacilli.  —  Schaffer  ^  was  able  to  recover  bacilli  from 
a  leprous  patient  by  holding  cover  glasses  a  short  distance  in 
front  of  the  face  while  the  patient  was  speaking  and  coughing. 
»  Schaffer,  Arch.  f.  Dermat.  u.  Syph.,  Wien,  1898,  XLIV,  159. 


298       THE  SOURCES  AND  MODES  OF  INFECTION 

Pneumococcus.  —  Wood  '  found  that  pneumococci  did  not 
retain  their  vitality  in  floating  droplets  over  one  hour,  and 
not  half  an  hour  in  diffused  light. 

Influenza  Bacilli.  —  According  to  Gotschlich,^  droplets  con- 
taining influenza  bacilli  will  float  for  five  hours.  Very  little 
has  been  done  to  demonstrate  the  existence  of  infected  drop- 
lets in  any  other  diseases. 

Bacteria  found  in  Air.  —  Having  shown  that  bacteria  may 
float  in  the  air  on  particles  of  dust  and  in  droplets  of  liquid, 
we  must  next  inquire  whether  pathogenic  germs  have  actually 
been  found  in  the  air.  Graham-Smith^  examined  the  air  of 
the  House  of  Commons  for  pathogenic  bacteria  with  negative 
results,  as  did  Andrewes^  and  Gordon^  the  air  in  the  streets 
of  London.  Little  light  is  thrown  on  our  present  problem 
by  these  and  similar  negative  tests  of  outdoor  air  or  of  air 
away  from  the  vicinity  of  the  sick.  Far  more  interest  and 
value  attach  to  the  examination  of  air  in  the  vicinity  of 
cases  of  infectious  sickness. 

Tubercle  Bacilli  in  Air.  —  Heymann"  was  able  to  recover 
virulent  tubercle  bacilli  from  the  air  of  a  small  chamber  in 
which  was  placed  a  coughing  tuberculous  patient-  Similar 
results  were  obtained  by  Laschtschenko.^  Corbett^  recovered 
acid-fast  bacilli  from  the  ventilating  shaft  of  a  hospital,  but 
made  no  inoculation  tests.  Klein"  infected  guinea  pigs  by 
exposure  in  the  vent  shaft  of  Brompton  Hospital.     According 

1  Wood,  J.  Kxpor.  M.,  N.  Y.,  1905,  VII,  r)92. 

2  Gotsclilich,  KoIIc  u.  Wasscrinann,  Mandbtich  [etc.],  Jena,  1902, 1, 175. 
'  Gruhani-SiniMi,  J.  Hyg.,  Cambridfro,  1903,  III,  498. 

*  Andrcwes,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1906-07, XXXVI, 
187. 

5  Gordon,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1902-03,  XXXII, 
421. 

8  Heymann,  Ztschr.  f.  llyK-  »•  Infection.skrankh.,  Leipz.,  1901, 
XXXVIII,  21. 

^  Laschtschenko,  Ztschr.  f.  llyg.  u.  Infection.skrankh.,  Lcipz.,  1899, 
XXX. 

"  Corh(!t,t,,  St.  Paul  M.  J.,  St.  Paul,  Minn.,  1904,  VI,  73r). 

"  Stevenson  and  Murphy,  Hygiene  and  Public  Health,  II,  212. 


INFECTION  BY  AIR  299 

to  Cornet  and  Meyer,^  Williams,  Celli  and  Guarnieri,  Wehde, 
and  Baumgarten  have  examined  air  for  tubercle  bacilli  with 
negative  results.  Recently  Le  Noir  and  Camus^  demon- 
strated by  inoculation  tubercle  bacilli  in  the  dust  of  a  hospi- 
tal ward,  but  they  could  not  obtain  them  by  the  filtration 
of  even  53,000  liters  of  the  air.  Viewing  the  human  nose  as 
a  filter,  they  took  swabbings  from  the  nose  of  physicians  and 
attendants  of  phthisical  patients,  but  could  not  demonstrate 
tubercle  bacilli  by  inoculation,  though  they  found  them  in 
the  nose  of  the  patients  themselves.  Cornet  considers  that 
the  germs  are  so  sparsely  distributed  that  one  ought  not  to 
expect  to  obtain  them  by  the  filtration  of  even  1000  liters 
of  air.  He  says  that  the  finding  of  tubercle  bacilli  in  settled 
dust  has  as  much  bearing  on  air  infection  as  finding  it  in 
the  air  and  is  a  much  easier  operation.  It  does  not  appear 
that  Cornet  is  correct  in  his  contention  that  the  examination 
of  dust  is  of  more  practical  importance  than  the  examination 
of  air.  The  examination  of  dust  can  throw  no  light  on  the 
number  of  bacteria  floating  in  the  air  at  any  one  time,  and 
as  Winslow  in  his  work  on  sewer  air  previously  referred 
to  has  so  clearly  pointed  out,  a  quantitative  examination  of 
the  floating  bacteria  is  necessary  if  we  wish  to  determine  the 
real  danger  from  the  inhalation  of  the  air.  No  such  enumer- 
ation of  tubercle  bacilli  seems  to  have  been  made,  and  the 
difficulty  of  finding  them  suggests  that  they  are  not  very 
numerous,  even  in  the  vicinity  of  patients,  and  that  perhaps 
the  air  of  a  room  is  not  always  dangerous  to  breathe  even  if 
tubercle  bacilli  can  be  found  in  the  settled  dust. 

Pus-forming  Bacteria  in  Air.  —  Numerous  observers  are 
referred  to  by  Gotschlich,^  Friedrich^  and  Noeggerath^  as 

1  Cornet  and  Meyer,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena, 
1903,  II,  143. 

2  Le  Noir  and  Camus,  Comp.  rend.  Soc.  de  biol.,  Par.,  1908,  LXV, 
464,  622;  Ann  d'hyg.  et  de  med.  colon.,  Par.,  1908,  4  s.,  IX,  74. 

'  Gotschlich, Kolle  u. Wassermann,  Handbuch  [etc.],  Jena,  1902,1, 176. 

*  Friedrich,  Arch.  f.  klin.  Chir.,  Berl.,  1898,  LVII,  288. 

'  Noeggeratb,  Deutsche  Ztschr.  f.  Chir.,  Leipz.,  1900-01,  LVIII,  277. 


300       THE  SOURCES  AND  MODES  OF  INFECTION 

having  found  various  pus-forming  bacteria  in  the  wards  and 
operating  rooms  of  the  hospitals.  Among  more  recent  Ameri- 
can writers  may  be  mentioned  Robb/  Rosenow,^  Monks  ^  and 
Harrington/  The  latter  found  that  Petri  dishes  exposed  in 
an  operating  room  in  Boston  always  contained  pus  organisms. 
The  maximum  was  131  per  square  inch  per  hour.  Gordon  ^ 
found  staphylococci  in  an  operating  room  in  England,  also  in 
a  barber's  shop,  and  they  have  been  demonstrated  in  the  air 
by  Hamilton.^  Gordon  could  not  find  them  in  the  open  air, 
but  they  have  been  found  in  the  air  of  streets  by  others.^ 

Other  Bacteria  in  Air.  —  Concornotti  ^  reports  that  he 
found  pneumonia  germs  in  the  air  of  the  Hygienic  Institute 
of  Cagliari. 

Beck  ®  found  swine  plague  bacilli  in  the  air  of  a  laboratory 
where  experiments  with  that  germ  were  being  carried  on. 

Bruce  ^"  could  not  find  the  germ  of  Mediterranean  fever  in 
air-borne  dust  in  Malta. 

Actual  Danger  of  Infection  by  Air.  —  Pathogenic  bacteria 
may  withstand  drying  and  the  pulverization  of  the  dried 
material,  and  they  may  be  actually  found  floating  in  the  air, 
yet  they  may  not  after  all  be  dangerous,  either  because  they 
have  wholly  or  partially  lost  their  virulence,  or  because  they 
are  too  few  in  number,  or  for  some  other  unknown  reason. 

Little  Infection  of  Wounds  by  Air.  —  It  has  been  shown 
that  notwithstanding  the  presence  of  considerable  numbers 

'  Robb,  Am.  J.  Obst.,  N.  Y.,  1909,  LX,  451. 

'  Rosenow,  Am.  J.  Obst.,  N.  Y.,  1901,  L,  762. 

3  Monks,  Ann.  Surg.,  Phila.,  1904,  XL,  466. 

*  Harrington,  Ann.  Surg.,  Phila.,  1904,  XL,  475. 

6  Gordon,  Rep.  Mod.  Off.  Local  Gov.  Bd.,  Lond.,  1904-05,  XXXIV, 
387. 

»  Hamilton,  .1.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  1108. 

^  Newman,  Bacteriology  and  the  Pub.  Health,  Lond.,  1904,  78. 

"  Concornotti,"  Centrlbl.  f.  Baktcriol.  [etc.],  Jena,  1899,  XXVI,  492. 

"  Beck,  .lahre.sl).  n.  d.  Fortschr.  .  .  .  d.  path.  Mik.,  Baumgarten, 
1891,  VII,  567. 

*»  Nature,  Lond.,  1908,  LXXVIII,  40. 


INFECTION  BY  AIR  301 

of  bacteria  in  the  air  of  operating  rooms,  the  aerial  infection 
of  wounds  is  of  no  practical  importance.  One  reason  for  this 
failure  to  infect  has  been  shown  by  Friedrich^  and  Noeg- 
gerath.^  The  conclusion  of  these  authors  is  that  drying  and 
exposure  to  light  so  weaken  the  bacteria  that  they  are  not 
able  to  withstand  the  actively  hostile  influences  of  the  tissues 
of  the  human  body,  though  they  may  be  able  slowly  to  vege- 
tate on  the  more  favorable  culture  media  of  the  laboratory. 
This  lowering  of  virulence  by  drying  and  exposure  to  light 
may  be  of  great  practical  moment  in  preventing  infection  by 
air.  So  also,  though  other  pathogenic  bacteria  may  be 
demonstrated  in  the  air,  it  may  be  that  they  are  usually 
too  few  in  number  to  infect. 

Experiments  with  Tuberculosis.  —  The  experiment  of 
Bernheim,^  in  which  he  was  not  able  to  infect  animals  with 
mouth  spray  over  25  cm.  from  the  mouth,  but  was  able  to 
collect  tubercle  bacilli  on  agar  plates  at  the  distance  of  a 
meter,  is  most  suggestive  of  the  importance  of  the  number 
of  bacteria  as  a  factor  in  infection.  The  proper  way  to  de- 
termine the  infectivity  of  the  air  is  by  animal  experiment 
or,  better  still,  by  carefully  conducted  observations  on  human 
beings.  Except  in  tuberculosis  very  few  experiments  of  this 
kind  have  been  made.  Much,  however,  has  been  done  with 
that  disease. 

Tappeiner*  had,  even  before  the  discovery  of  the  tubercle 
bacillus,  shown  that  tuberculosis  could  be  produced  in  dogs 
by  causing  them  to  breathe  dry  and  pulverized  tuberculous 
sputum.  Bertheau,  Veraguth,  Weichselbaum  and  Frerich, 
like  Tappeiner,  succeeded  in  infecting  animals  by  causing 
them  to  inhale  pulverized  sputum  containing  tubercle  bacilli, 
while  Koch,  Cornet,  Gebhardt  and  Preyss  accomplished  the 

1  Friedrich,  Arch.  f.  klin.  Chir.,  Berl.,  1898,  LVII,  288. 

2  Noeggerath,  Deutsche  Ztschr.  f.  Chir.,  Leipz.,  1900-01,  LVIII,  277. 

3  Bernheim,  CHnique,  Brux.,  1905,  XIX,  346. 

^  Tappeiner,  Virchow's  Arch.  f.  path.  Anat.  [etcl,  Berl.,  1880, 
LXXXII,  353. 


302       THE  SOURCES  AND  MODES  OF  INFECTION 

same  results  by  the  use  of  dried  bacilli  obtained  from  cul- 
tures. More  recently  Cornet '  reports  a  still  more  striking 
experiment.  In  a  room  of  seventy-six  cubic  meters  capacity, 
48  guinea  pigs  were  exposed  in  cages  at  various  heights 
above  the  floor.  Sputum  was  placed  on  a  carpet,  and  after 
it  was  dry  the  carpet  was  shaken  so  that  the  dust  rose  up 
in  clouds.  This  was  repeated  on  four  days.  The  result  was 
that  47  of  the  48  animals  developed  tuberculosis  within  two 
months.  Kuss  ^  carried  on  experiments  very  similar  to  those 
of  Cornet  and  with  similar  results.  Kohlisch,^  while  admit- 
ting that  tuberculosis  maybe  caused  by  the  inhalation  of  dust, 
claims  that  his  experiment  shows  that  enormously  larger 
quantities  must  be  inhaled  than  are  necessary  when  a  spray 
is  employed.  While  B.  prodigiosus  is  not  pathogenic,  it  has 
been  used  by  various  workers  for  studying  the  penetration 
of  bacteria  into  the  respiratory  tract.  Nenninger,^  using 
both  infected  dust  and  a  sprayed  culture,  found  that  the 
germs  were  quickly  carried  to  the  smallest  bronchioles. 

Dust  Infection  Questioned.  —  The  contention  that  pul- 
monary tuberculosis  maj^  be  caused  by  the  inhalation  of  dust 
containing  tubercle  bacilli  was  not  to  go  unchallenged.  Sirena 
and  Pernice,  de  Toma,  Celli  and  Guarnieri,  and  Cadeac  and 
Malet  were  unsuccessful  in  their  attempts  to  produce  the 
disease  in  this  way.  But  perhaps  Fliigge^  more  than  any 
other  has  cast  discredit  on  this  theory  of  the  origin  of  pul- 
monary tuberculosis.  He  was  unable  to  induce  infection  by 
causing  animals  to  inhale  tuberculous  dust,  and  states  that  the 
dust  is  not  carried  to  the  alveoli.  He  also  developed  the 
theory  of  droplet  infection,  which  has  been  received  with  much 

»  Cornet,  Vorhandl.  d.  Borl.  mod.  Gesollsch.,  1899,  XXX,  2  Th.,  91. 

2  Kuss,  Sixth  Iiitornat.  (>)ng.  on  TuJ)orc.,  Wash.,  190S,  I,  101. 

'  Kohlisch,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1908,  LX, 
508. 

*  Ncnningor,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1901, 
XXXVIII,  94. 

^  Fliigge,  Ztschr.  f.  Hyg.  u.  Infectionekrankh.,  Leipz.,  1899,  XXX, 
107. 


INFECTION  BY  AIR  303 

favor,  and  did  much  to  break  down  the  almost  universal 
view  that  dust  is  the  chief  vehicle  of  infection  in  this  disease. 
Again  when  Koch  in  1901  by  his  pronunciamento,  that  human 
tuberculosis  is  never  caused  by  the  milk  of  tuberculous  ani- 
mals, stimulated  a  great  number  of  workers  to  attempt  to 
prove  the  contrary,  evidence  began  to  accumulate  that  tuber- 
culous infection  of  the  lungs  might  be  brought  about  in  vari- 
ous ways,  and  facts  came  to  light  which  told  against  the  view 
that  direct  infection  by  means  of  dust  is  the  only  manner 
in  which  pulmonary  tuberculosis  can  be  caused. 

Dust  versus  Droplets.  ■ —  According  to  the  school  of  Fliigge, 
infection  by  droplets  is  much  more  likely  to  take  place  than 
infection  by  dust,  and  his  pupils  have  demonstrated  the 
presence  of  the  bacilli  in  the  lungs  immediately  after  inhala- 
tion. Findel,^  working  in  his  laboratory,  has  shown  that  the 
inhalation  of  even  so  small  a  number  as  62  germs  is  sufficient 
to  cause  the  disease,  and  he  asserts  that  several  million  times 
as  many  bacteria  are  necessary  to  infect  when  taken  by  the 
stomach.  Laschtschenko^  and  Heymann,^  working  under 
the  direction  of  Fliigge,  were  able  to  infect  guinea  pigs  with 
tuberculosis  by  causing  them  to  breath  directly  in  front  of  the 
mouth  of  phthisical  patients  while  the  latter  were  coughing. 
The  pigs  were  not  infected  when  distant  over  one  meter. 
Fliigge  ^  himself  infected  6  of  25  guinea  pigs  in  this  manner, 
holding  them  distant  from  twenty  to  forty-five  cm.  from  the 
mouth  of  the  patient.  Pfeiffer  and  Friedberger  ^  sprayed 
guinea  pigs  with  a  culture  containing  35,000  tubercle  bacilli  to 

1  Findel,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1907,  LVII, 
104. 

*  Laschtschenko,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899, 
XXX,  125. 

^  Heymann,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
139. 

*  Fliigge,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
107. 

^  Pfeiffer  and  Friedberger,  Deutsche  med.  Wchnschr.,  1907,  XXXIII, 
1577. 


304       THE  SOURCES  AND  MODES  OF  INFECTION 

the  c.c.  The  animals  were  held  for  ten  minutes  at  a  distance 
of  eight  to  twenty  cm.  in  such  a  manner  that  their  bodies 
were  perfectly  protected.  Those  held  at  the  greater  distance 
did  not  contract  tuberculosis,  but  the  others  developed  what 
appeared  to  be  primary  tuberculosis  of  the  lungs.  Bartel 
and  Neumann/  after  spraying  guinea  pigs  with  tubercle 
bacilli,  found  the  germs  immediately  in  mouth,  throat  and 
lungs.  Bernheim^  infected  guinea  pigs  at  the  distance  of 
not  over  twenty-five  cm.,  but  he  was  able  to  collect  tubercle 
bacilli  on  agar  plates  at  the  distance  of  one  meter  from  the 
mouth.  So  also  Kuss  and  Lobstein,^  carrying  out  very  care- 
ful inhalation  experiments  with  a  sprayed  culture  of  tubercle 
bacilli,  very  easily  and  constantly  developed  pulmonary 
disease.  Kovacs,*  after  inhalation  experiments  with  tubercle 
bacilli,  could  immediately  recover  them  from  the  lungs.  But 
he  thinks  that  they  may  also  pass  from  the  mouth  to  the 
lungs  via  the  cervical  and  bronchial  glands.  Cobbett,''  em- 
ploying sprays  both  of  B.  prodigiosus  and  of  the  tubercle 
bacillus,  reports  that  the  bacteria  are  carried  to  the  periph- 
ery of  the  lungs  by  the  inspired  air. 

The  Inhalation  of  Bacteria.  —  On  the  other  hand,  Hewlett 
and  Thompson"  found  that  inhaled  bacteria  were  not  carried 
even  as  far  as  the  trachea,  as  Hildebrandt  ^  had  found  before. 
Hartl  and  Herrmann^  showed  that  inhaled  germs  decreased 
very  rapidly  back  from  the  nose,  and  they  consider  that  the 
upper  passages  are  frequently  the  place  of  entrance  for  the 
infection,  and  that  bacteria  are  rarely  carried  by  the  air  to 

»  Bartel  and  Neumann,  Wien.  klin.  Wchnschr.,  1906,  XIX,  167,  213. 
2  Bernheim,  Clinique,  Brux.,  1905,  XIX,  346. 
'  Kuss  and  Lobstcin,  Bull,  med.,  Paris,  1907,  XXI,  821. 
*  Kovdos,  Beitr.  z.  path.  Anat.  u.  ■/..  allg.  Path.,  Jena,  1906,  XL,  281. 
»  Brit.  M.  J.,  Lond.,  1909,  II,  867. 
8  Hewlett  and  Thompson,  Lancet,  Lond.,  1896,  I,  86. 
^  Hildebrandt,  Beitr.  z.  path.  Anat.  u.  z.  allp;.  Path.,  Jena,  1887,  II, 
411. 

'  Hart!  and  Herrmann,  Wien.  klin.  Wchnschr.,  1905,  XVIII,  798. 


INFECTION  BY  AIR  305 

the  lungs.  Vallee  ^  carried  on  spray  experiments  without 
result,  and  Calmette  and  Guerin/  in  a  few  experiments  made 
with  infected  dust,  did  not  find  that  the  bacilli  reached  the 
alveoli.  Weleminsky^  could  find  no  bacilh  in  the  lungs  of 
guinea  pigs  immediately  after  they  had  been  subjected  to 
inhalation  experiments. 

Lack  of  Agreement  among  Investigators.  —  Thus  it  is  seen 
that  the  school  of  Cornet  claims  that  pulmonary  tuberculosis 
is  almost  always  caused  by  the  passage  of  infected  dust  to  the 
alveoli,  and  that  infected  droplets  are  of  little  moment;  while 
Fliigge  and  his  pupils  attempt  to  show  that  dust  rarely  reaches 
the  alveoli  but  that  the  inhalation  of  droplets  is  the  easiest 
method  of  causing  the  disease.  The  unprejudiced  reader 
must  conclude  that  infection  in  either  way  is  possible,  but 
the  conditions  of  the  experiments  are  so  far  removed  from  the 
natural  that  there  must  be  much  hesitation  before  assuming 
that  this  work  indicates  in  any  degree  the  common  mode  of 
infection  in  human  beings. 

Bacilli  may  pass  from  Stomach  to  Lungs.  —  It  is  com- 
monly assumed  that  because  pulmonary  tuberculosis  begins 
in  the  apices  of  the  lungs  the  bacilli  must  be  carried  directly 
to  the  alveoli  by  the  inspired  air.  Moreover  most  patholo- 
gists consider  that  evidence  points  to  the  alveolar  surface  as 
the  starting  point  of  the  disease,  and  that  the  relative  age  of 
the  lesions  in  the  lungs  and  the  glands  indicates  that  it  is 
primarily  a  pulmonary  disease.  The  writer  is  not  competent 
to  discuss  the  findings  of  the  pathologists,  but  there  are  a 
large  number  of  careful  observers  who  believe  on  pathological 
and  experimental  evidence  that  the  bacilli  which  cause  pul- 
monary tuberculosis  may  find  their  way  through  the  lymph 
and  the  blood  from  any  part  of  the  alimentary  tract  to  the 
lungs.  Some  pathologists  believe  that  the  disease  begins 
in  the  capillaries  rather  than  in  the  alveoli.     Calmette  and 

»  Vallee,  Ann.  d.  I'Inst.  Pasteur,  1905,  XIX,  619. 

2  Calmette  and  Guerin,  Ann.  de  I'Inst.  Pasteur,  1905,  XIX,  601. 

»  Weleminsky,  Berl.  klin.  Wchnschr.,  1905,  XLII,  743. 


306       THE  SOURCES  AND  MODES  OF  INFECTION 

Guerin '  say  that  primary  tubercle  of  the  lungs  always  be- 
gins in  the  capillaries,  and  never  in  the  alveoli,  and  Aufrecht  ^ 
from  his  pathological  studies  comes  to  the  same  conclusion. 

Even  pulmonary  anthracosis  may  be  caused  by  the  inges- 
tion of  particles  of  carbon.  Vansteenburgh  and  Grysez ' 
caused  animals  to  breath  air  loaded  with  soot  from  a  smoky 
lamp,  and  though  the  nose  was  filled  with  soot,  none  was  found 
in  lungs  or  even  trachea.  If  the  experiment  was  prolonged, 
carbon  appeared  in  the  lungs,  but  not  if  the  esophagus  was  tied. 
When  one  bronchus  was  occluded,  the  carbon  appeared  in  the 
parenchyma  of  the  lung  just  the  same,  provided  the  esoph- 
agus was  open.  Whitla^  fed  animals  with  carbon  and  bacilli, 
and  both  were  found  in  the  lungs  in  from  four  to  twenty-four 
hours.  Feeding  was  done  with  a  tube,  with  great  care  to 
prevent  inhalation.  Hutchens  ^  fed  guinea  pigs  with  coal 
dust,  and  also  injected  it  into  the  abdomen,  and  found  it  in 
the  lungs  in  three  days.  Grober,®  after  injecting  India  ink 
into  the  tonsils,  was  able  to  find  the  pigment  in  the  lungs 
in  a  short  time.  He  thought  that  he  could  trace  a  continu- 
ous lymphatic  route  from  the  tonsils  to  the  costal  pleura, 
whence  the  particles  passed  directly  to  the  parietal  pleura 
and  the  lungs.  But  such  a  connection  has  been  denied  by 
Beitzke,'  Wood  ^  and  others. 

Schultze  ®  denies  that  pulmonary  anthracosis  can  be  pro- 

»  Calmette  and  Gu6rin,  Ann.  de  I'lnst.  Pasteur,  1906,  XX,  609. 

»  Aufrecht,  Deutsches  Arch.  f.  klin.  Med.,  Leipz.,  190S,  XCIV,  308. 

'  Vansteenburgh  and  Grysez,  Ann.  de  I'lnst.  Pasteur,  1905,  XIX,  787. 

*  Whitla,  Brit.  M.  J.,  Lond.,  1908,  II,  61. 

s  Cited  by  Ohver,  Brit.  M.  J.,  Lond.,  1908,  II,  481. 

'  Grober,  Die  Tonsillen  als  Eintrittspforten  fiir  Krankheitserreger, 
Abdruck  aus  dem  klin.  Jahrb.,  Berl.,  1905,  XIV,  547. 

'  Beitzke,  Virchow'sArch.f.  path.  Anat.  [etc.],  Berl.,  1906,  CLXXXIV, 
1;  Berl.  klin.  Wchns(;hr.,  1908,  XLV,  12.35. 

'  Wood,  Rep.  Ilcnry  Phipps  In.st.  Study  .  .  .  Tuberculosis,  Phila., 
1906,  IV,  lO.-}. 

•  Schultze,  Munchen  mod.  Wclmsclir.,  1906,  LIII,  1702. 


INFECTION  BY  AIR  307 

duced  by  feeding,  as  is  claimed  by  the  French  experimenters, 
and  insists  that  during  the  feeding  some  inhalation  takes  place, 
and  that  if  the  animals  are  fed  through  a  gastric  fistula  with 
adequate  precautions,  the  fragments  are  not  carried  to  the 
lungs. 

A  large  number  of  workers  have  certainly  demonstrated 
that  pulmonary  tuberculosis  may  be  caused  by  infection 
through  different  portions  of  the  alimentary  canal. 

The  work  of  Calmette  and  Guerin  ^  shows  that  tubercle 
bacilli  are  speedily  carried  from  the  intestines  to  the  lungs. 

Schroeder  and  Cotton^  have  shown  that  pulmonary  disease 
develops  no  matter  in  what  part  of  the  body  tubercle  bacilli 
are  inoculated,  and  in  Bulletin  88  they  have  shown  that 
marked  pulmonary  invasion  occurs  constantly  in  hogs  fed  on 
tuberculous  material.  So  also  Ravenel  ^  has  recovered  tu- 
bercle bacilli  from  the  lungs  within  a  few  hours  after  placing 
them  in  the  stomach  by  celiotomy.  Beitzke^  in  a  review  of 
the  subject  states  that  Schlossmann  and  St.  EngeP  found  the 
bacilli  in  the  lungs  six  hours  after  injection  into  the  stomach 
by  laparotomy,  as  did  also  L.  Rabinowitsch,  and  that  the 
latter  and  also  Uffenheimer,  Bacharach,  and  Stein  and  Orth 
found  them  after  injection  into  the  intestine.  Ficker,  he  says, 
could  not  do  this  with  adult  dogs  or  cats,  and  Herrmann  could 
not  with  monkeys.  Vallee,**  Calmette  and  Guerin,^  Bonome  ' 
and  Arloing  **  also  have  demonstrated  pulmonary  infection 

1  Calmette  and  Guerin,  Ann.  de  I'lnst.  Pasteur,  1905,  XIX,  601; 
1906,  XX,  353,  609. 

5  Schroeder  and  Cotton,  U.  S.  Dept.  Agric.  Bu.  An.  Ind.  Bull.  No.  86 
and  No.  93. 

'  Ravenel,  Cleveland  M.  J.,  1909,  VIII,  179. 

*  Beitzke,  Berl.  klin.  Wchnschr.,  1908,  XLV,  1235. 

^  Schlossmann  and  St.  Engel,  Deutsche  med.  Wchnschr.,  1906, 
XXXII,  1070. 

«  Vallee,  Ann.  de  I'lnst.  Pasteur,  1905,  XIX,  619. 

^  Bonome,  Gazz.  d.  osp.,  Milano,  1907,  XXVIII,  Nos.  37-84,  abstract 
in  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  888. 

'  Arloing,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  IV,  666. 


308       THE  SOURCES  AND  MODES  OF  INFECTION 

via  the  alimentary  tract,  and  very  many  of  the  experiments 
have  shown  that  the  bacilli  easily  pass  through  the  intestinal 
wall  without  leaving  a  trace  of  their  passage,  so  that  the 
absence  of  lesion  of  the  alimentary  tract  is  no  proof  that 
infection  has  not  taken  place  through  it. 

Unnatural  Conditions  of  Experiment.  —  Although  there 
has  been,  as  is  here  shown,  a  vast  amount  of  experimental 
work  on  infection  with  tuberculosis,  there  has  been  very  little 
in  which  the  conditions  at  all  approached  the  natural.  Usu- 
ally there  is  an  excessive  amount  of  exposure,  or  an  excessive 
number  of  germs  in  spray  or  dust.  Thus  in  Cornet's  nota- 
ble experiment,  where  47  of  48  guinea  pigs  were  infected  by 
breathing  dust,  the  carpet  had  been  smeared  with  large 
quantities  of  sputum,  and  it  was  forcibly  beaten  so  that 
clouds  of  dust  rose  up  directly  in  front  of  the  animals.  It  is 
surprising  that  so  few  have  thought  it  worth  while  to  see 
how  infection  takes  place  in  animals  kept  under  conditions 
as  nearly  as  possible  like  those  under  which  human  beings 
live. 

Infection  in  Laboratory.  —  Animals  kept  in  laboratories  in 
company  with  others  that  have  been  purposely  infected  rarely 
contract  the  disease.  Koch'  in  his  original  paper  says  that 
among  the  hundreds  of  animals  so  kept  the  disease  did  not 
develop  for  three  or  four  months,  and  then  only  exception- 
ally. He  reports  autopsies  on  17  guinea  pigs  and  8  rabbits 
thus  naturally  infected,  which  showed  in  all  cases  a  pul- 
monary tuberculosis  resembling  that  which  occurs  in  man. 
But  apparently  no  effort  was  made  to  determine  whether 
infection  was  by  the  air,  by  the  food,  or  by  contact  through 
the  hands  of  attendants,  though  this  laboratory  infection  has 
been  urged  as  evidence  that  the  disease  is  air-borne.  Of  many 
hundreds  of  guinea  pigs  confined  in  a  room  with  various 
tuberculous  animals  in  the  Department  of  Agriculture  Ex- 
periment Station  at  Washington,  only  one  contracted  tuber- 

*  Kooh,  Mit.  a.  d.  k.  Gosund.-Anit.,  1884,  II,  Trans.  Sydenham  Soc. 
Pub.,  CXV,  129. 


INFECTION  BY  AIR  309 

culosis,  and  that  was  in  a  cage  with  several  infected  animals.^ 
In  laboratories  floating  bacteria  are  not  likely  to  be  very  nu- 
merous, owing  to  the  cleanliness  practiced  and  the  fact  that 
most  of  the  laboratory'  animals  do  not  excrete  many  bacilli. 
Experiments  under  Natural  Conditions.  Tuberculosis.  ^ 
Schroeder  and  Cotton^  experimented  under  more  natural 
conditions.  Seven  cows  were  exposed  in  adjoining  stalls  to 
3  tuberculous  animals,  and  all  but  1  of  them  contracted  the 
disease.  As  all  but  2  were  moved  about  from  stall  to  stall, 
exchanging  with  the  infected  animals,  infection  may  readily 
have  been  by  contact.  At  the  same  time  100  guinea  pigs 
were  exposed  in  the  stalls,  one  half  in  cages  below  the  man- 
gers where  food  could  sift  through  from  the  mangers,  and 
one  half  on  the  walls.  The  exposure  lasted  several  months, 
and  only  1  of  the  pigs,  in  a  cage  under  the  manger,  became 
infected.  In  a  subsequent  experiment  35  guinea  pigs  were  ex- 
posed for  one  hundred  and  thirty-five  days  on  the  walls  of 
the  stalls.  Two  developed  generalized  tuberculosis.  Of  42 
animals  kept  for  fifty-one  days  under  the  manger  of  infected 
cows,  6  developed  a  more  or  less  generalized  type  of  the 
disease.  There  was  no  direct  evidence  that  tubercle  bacilli 
were  in  the  air  of  the  stalls,  but  as  the  infecting  animals 
were  excreting  large  numbers  of  bacilli,  there  is  little  doubt 
of  it.  There  is  no  record  that  contact  infection  from  the 
hands  of  attendants  was  strictly  guarded  against,  and  it  may 
be  that  the  2  out  of  135  guinea  pigs,  and  the  2  cows  supposed 
to  have  succumbed  to  air-borne  infection,  were  really  infected 
by  contact.  Swenson,  quoted  by  Aufrecht,  exposed  five 
calves  in  a  stable  with  tuberculous  cows  in  such  a  manner  as 
to  preclude  contact  infection,  and  they  all  developed  the 
disease,   as  Swenson  thought,  by  dust  infection.      Klein  ^ 

1  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  Wash.,  1906,  XXIII,  31. 

*  Schroeder  and  Cotton,  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind., 
Wash.,  1903,  XX,  61;  1904,  XXI,  44,  reprinted  as  Circ.  No.  83. 

'  Stevenson  and  Murphy,  Treatise  on  Hygiene  and  Public  Health, 
Lond.,  1893-96,  II,  212. 


310       THE  SOURCES  AND  MODES  OF  INFECTION 

exposed  guinea  pigs  in  the  vent  shaft  of  the  Brompton  Hos- 
pital, and  most  of  them  contracted  tuberculosis. 

Experiments  in  Tuberculosis  Houses.  —  Bartel  and  Spieler,^ 
realizing  that  most  experiments  are  under  unnatural  con- 
ditions, exposed  12  guinea  pigs  in  cages  in  a  house  occupied 
by  tuberculous  patients,  and  allowed  16  to  run  at  large  and 
be  handled  by  the  children.  The  exposure  was  from  two  to 
three  weeks,  and  of  the  12  cage  pigs  3  developed  tubercu- 
losis, and  of  the  16  free  pigs  10  developed  tuberculosis  of 
various  glands  and  other  organs.  No  statement  is  made 
that  care  was  taken  to  prevent  contact  or  mouth-spray  in- 
fection of  the  animals  in  the  cages.  These  authors  ^  exposed 
8  guinea  pigs,  running  free,  in  a  house  where  the  tuberculous 
patient  was  taking  fairly  good  care  of  the  sputum.  Only  1 
of  the  guinea  pigs  developed  tuberculosis. 

At  my  suggestion  Dr.  M.  S.  Packard  of  Providence  carried 
on  an  experiment  for  the  health  department  of  that  city  on 
the  mode  of  infection  of  guinea  pigs  under  natural  conditions. 
A  fairly  clean  laborer's  house  was  chosen,  where  there  was  a 
consumptive  whose  sputum  contained  large  numbers  of  ba- 
cilli, and  who  was  taking  no  care  whatever  in  regard  to  its 
disposal.  Thirty-six  small  guinea  pigs  were  exposed  in  cages 
placed  in  a  dark  place  in  the  room  in  which  the  patient  usually 
sat.  The  cages  were  much  crowded.  Of  the  animals,  16 
were  fed  and  cared  for  by  the  consumptive,  and  the  others 
by  an  employee  of  the  department  free  from  disease.  These 
latter  animals  were  locked  in  a  box  covered  with  wire  net- 
ting, fourteen  meshes  to  the  inch.  There  could  be  no  ques- 
tion of  contact  infection  for  these  pigs.  The  exposure  was 
from  February  11,  1908,  to  May  14.  All  but  21  of  the 
animals  died  of  non-tubor(;ulous  disease,  or  were  starved  or 
killed  by  rats  aft(^r  removal  from  the  house.  Of  the  11 
surviving  animals  exposed  to  air  infection  alone,   8  were 

1  Bartel  and  Spiclor,  Wien.  klin.  Wchnschr.,  1905,  XVIII,  218. 
^  Festschr.  onthalt.  All),  u.  Tuhork.  .  .  .  VI  Intenuit.  Tubcrk.  Konf. 
[etc.],  Wien  u.  Leipz.,  1907,  71. 


INFECTION  BY  AIR  311 

shown  to  be  tuberculous  and  3  not  tuberculous.  Of  the 
other  lot,  7  were  shown  to  be  tuberculous  and  3  not.  It 
seems  impossible  that  the  test  animals  could  have  been  in- 
fected otherwise  than  through  the  air.  That  it  was  mouth 
spray  rather  than  dust  infection  seems  likely,  for  the  patient 
took  much  interest  in  the  animals,  and  was  often  seen  with 
his  face  close  to  the  netting,  talking  to  them,  and  coughing  at 
them  only  a  few  inches  distant.  The  guinea  pigs  were  pur- 
chased, but  I  was  unable  to  learn  that  they  had  ever  been 
exposed  to  the  disease. 

Since  writing  the  above  I  note  that  Le  Noir  and  Camus  * 
have  undertaken  a  similar  experiment.  They  exposed  guinea 
pigs  in  cages  in  a  ward  for  phthisical  patients.  Four  pigs 
were  placed  in  a  cage  on  the  floor  and  the  patients  fed  these. 
One  of  them  developed  tuberculosis.  Five  pigs  were  kept 
for  six  weeks  in  a  cage  on  the  floor  but  protected  so  that  the 
patients  could  not  reach  them.  One  of  these  also  developed 
tuberculosis.  Another  pig  with  three  little  ones  was  placed 
in  a  cage  near  the  ceiling  so  that  they  had  to  be  fed  from  a 
ladder.  One  of  the  little  ones  died  of  an  intercurrent  affec- 
tion, but  the  other  two  contracted  tuberculosis. 

Since  it  is  claimed  by  the  majority  of  those  interested  in 
tuberculosis  that  the  disease  is  spread  chiefly  by  means  of 
dust,  it  is  highly  desirable  that  a  sufficient  number  of  well- 
conducted  experiments  under  truly  natural  conditions  be 
made  to  determine  how  important  this  mode  of  infection 
really  is. 

Except  for  tuberculosis  very  little  animal  experimentation 
has  been  done  to  determine  whether  diseases  are  air-borne. 
One  reason  for  this,  of  course,  is  that  so  many  of  the  com- 
moner diseases  affecting  human  beings  are  not  easily  con- 
tagious for  the  lower  animals. 

Experiments  with  Mediterranean  Fever.  —  Horrocks,^ 
experimenting  with   monkeys,   could    cause  Mediterranean 

1  Le  Noir  and  Camus,  Presse  med.,  Par.,  1909,  XVII,  761. 
*  Horrocks,  Report  of  Royal  Commission  on  Malta  Fever. 


312       THE  SOURCES  AND  MODES  OF  INFECTION 

fever  by  making  the  animals  inhale  dust  artificially  infected 
with  large  numbers  of  M.  melitensis,  but  he  was  not  successful 
with  dust  naturally  infected  with  urine,  though  the  organism 
of  this  disease  is  very  resistant  to  drying.  Monkeys  kept  in 
cages  near  infected  animals  did  not  contract  the  disease, 
unless  there  was  actual  contact  with  infected  material,  i.e., 
there  was  no  air-borne  infection.  Epidemiological  evidence 
is  against  this  being  a  dust  disease,  for  it  prevails  far  less 
during  the  dry  than  during  the  wet  season.  That  it  is  in 
reality  exclusively  milk-borne  seems'  now  to  have  been 
demonstrated. 

Experiments  with  Anthrax.-  —  Biichner  ^  was  the  first  to 
attempt  to  infect  animals  by  making  them  breathe  dried 
anthrax  bacilli  or  spores.  He  easily  succeeded  in  thus  caus- 
ing primary  pulmonary  disease.  Miiskatbliith  ^  showed  that 
the  spores  would  readily  pass  the  lungs  without  causing  local 
disease.  Morse,  Hildebrandt,  Tschistovitsch  and  Gramat- 
schikoff  ^  could  not  cause  the  disease  by  inhalation  even 
when  the  spray  was  sent  directly  into  the  trachea.  Baum- 
garten^  believes  that  these  various  experiments  show  that 
infection  takes  place  by  the  tonsils  rather  than  directly  by 
the  lungs. 

Experiments  with  Plague.  —  Bubonic  plague  is  often  con- 
sidered an  air-borne  disease,  but  the  experiments  of  the  present 
Indian  Plague  Commission^  have  shown  that  this  is  not  the 
case.  Both  monkeys  and  guinea  pigs  have  in  considerable 
numbers  been  put  in  flea-proof  cages,  but  exposed  freely  to 
the  air,  and  the  cages  plac(Hl  in  dwellings  known  to  be  in- 
fected, and  in  no  instance  did  they  contract  the  disease.  In 
other  instances  the  animals  were  exposed  freely  to  the  air,  but 

>  Biichner,  Contrlbl.  f.  Bakteriol.  [etc.],  Jona,  1890,  VII,  733; 
VIII,  1. 

2  Miiskatbluth,  Centrlbl.  f.  Bakteriol.  [etc.],  Jena,  1887,  I,  321. 

^  Cited  by  Sobernheim  in  KoUe  u.  Wasscrmann  Handbuch  [etc.], 
Jena,  1903,  II,  49. 

*  Lehrbuch  d(>r  PatliolofriHclicii  Mycoloj^ic,  liraunschweig,  1890. 

"^  Journal  Ilygicac,  1905,  S35;  1900,  445-171;  1907,  432,  835,  979. 


INFECTION  BY  AIR  313 

were  protected  from  fleas  by  "  tangle-foot,"  with  like  results. 
These  experiments  were  made  at  various  times  and  places, 
but  the  animals  never  succumbed  to  air-borne  infection.  In 
all  instances  control  animals  not  protected  from  fleas  usually 
contracted  the  disease. 

Conclusions.  —  After  the  foregoing  survey  of  the  subject 
we  are,  I  think,  justified  in  the  following  conclusions: 

1.  The  theory  of  the  aerial  transmission  of  disease  was 
developed  as  the  most  reasonable  way  of  explaining  the  phe- 
nomena of  infection. 

2.  Contact  infection  with  carriers  and  missed  cases  affords 
a  better  explanation  of  the  phenomena. 

3.  The  best  medical  thought  has  been  steadily  restricting 
the  supposed  sphere  of  aerial  transmission. 

4.  Only  a  few  authorities  now  assert  that  disease  is  carried 
by  the  atmosphere  outside  of  dwellings,  and  this  assertion  is 
made  only  in  regard  to  smallpox. 

5.  Bacteriology  teaches  that  former  ideas  in  regard  to  the 
manner  in  which  diseases  may  be  air-borne  are  entirely  erro- 
neous; that  most  diseases  are  not  likely  to  be  dust-borne, 
and  they  are  spray-borne  only  for  two  or  three  feet,''a  phe- 
nomenon which  after  all  resembles  contact  infection  more 
than  it  does  aerial  infection  as  ordinarily  understood. 
Tuberculosis  is  more  likely  to  be  air-borne  than  is  any  other 
common  disease. 

6.  Surgeons  at  first  developed  aseptic  surgery  on  the  theory 
that  air  infection  was  of  the  highest  importance.  They  have 
gradually  learned  to  pay  less  attention  to  it,  until  at  present 
some  of  the  best  surgeons  consider  it  a  negligible  factor. 

7.  Animal  experimentation  indicates  that  tuberculosis  and 
anthrax  may  be  air-borne,  and  that  plague  and  some  other 
diseases  are  not. 

8.  Pathology  has  not  determined,  as  is  sometimes  alleged, 
that  even  pulmonary  consumption  is  an  air-borne  disease. 

9.  There  is  no  good  clinical  evidence  that  the  common 
diseases  are  air-borne. 


314       THE  SOURCES  AND  MODES  OF  INFECTION 

10.  There  is  considerable  clinical  evidence  that  scarlet 
fever,  diphtheria,  smallpox,  measles,  whooping  cough,  typhoid 
fever  and  plague  are  not  easily  transmissible  through  the  air. 

11.  Scarlet  fever  and  diphtheria  can  be  cared  for  in  the 
same  ward  with  other  diseases  without  extension,  if  clean- 
liness be  maintained  and  infection  by  contact  avoided. 

In  reviewing  the  subject  of  air  infection  it  becomes  evident 
that  our  knowledge  is  still  far  too  scanty,  and  that  the  avail- 
able evidence  is  far  from  conclusive.  Yet  it  is  of  the  greatest 
practical  importance  that  we  should  know  definitely  just  what 
danger  there  is  of  air-borne  infection  and  in  what  diseases 
it  is  to  be  feared.  Infection  by  air,  if  it  does  take  place,  as  is 
commonly  believed,  is  so  difficult  to  avoid  or  guard  against, 
and  so  universal  in  its  action,  that  it  discourages  effort  to 
avoid  other  sources  of  danger.  If  the  sick-room  is  filled  with 
floating  contagium,  of  what  use  is  it  to  make  much  of  an  effort 
to  guard  against  contact  infection?  If  it  should  prove,  as  I 
firmly  believe,  that  contact  infection  is  the  chief  way  in  which 
the  contagious  diseases  spread,  an  exaggerated  idea  of  the 
importance  of  air-borne  infection  is  most  mischievous.  It  is 
impossible,  as  I  know  from  experience,  to  teach  people  to 
avoid  contact  infection  while  they  are  firmly  convinced  that 
the  air  is  the  chief  vehicle  of  infection. 

While  it  is  not  possible  at  present  to  state  with  exactness 
the  part  played  by  aerial  infection  in  the  transmission  of  the 
different  infectious  diseases,  we  are  by  the  evidence  forced  to 
the  conclusion  that  the  current  ideas  in  regard  to  the  impor- 
tance of  infection  by  air  are  unwarranted.  Without  denying 
the  possibility  of  such  infection,  it  may  be  fairly  affirmed 
that  there  is  no  evidence  that  it  is  an  appreciable  factor  in 
the  maintenance  of  most  of  our  common  contagious  diseases. 
We  are  warranted,  then,  in  discarding  it  as  a  working  hy- 
pothesis and  devoting  our  chief  attention  to  the  prevention 
of  contact  infection.  It  will  be  a  great  relief  to  most  persons 
to  be  freed  from  the  specter  of  infected  air,  a  specter  which 
has  pursued  the  race  from  the  time  of  Hippocrates,  and  we 


INFECTION  BY  AIR  315 

may  rest  assured  that  if  people  can  as  a  consequence  be 
better  taught  to  practice  strict  personal  cleanliness,  they  will 
be  led  to  do  that  which  will  more  than  anything  else  prevent 
aerial  infection  also,  if  that  should  in  the  end  be  proved  to  be 
of  more  importance  than  now  appears. 


CHAPTER  VII. 

INFECTION    BY    FOOD  AND    DRINK. 

Infection  by  Water. 

.  Broad  Street  Well. — From  time  immemorial  water  has  been 
believed  to  be  the  bearer  of  disease,  but  it  is  only  since  the 
middle  of  the  nineteenth  century  that  the  subject  has  been 
scientifically  studied.  One  of  the  first  instances  of  a  clear- 
cut  demonstration  of  the  causation  of  sickness  by  infected 
water  was  that  of  the  now  famous  Broad  Street  well,  so  ably 
studied  by  Snow.^  During  the  outbreak  of  cholera  in  Lon- 
don in  1854  there  was  an  enormous  concentration  of  cases 
in  a  very  limited  area  just  east  of  Regent  Street,  there  having 
been  reported,  during  a  period  of  about  six  weeks,  over  600 
fatal  cases,  A  careful  study  of  the  site,  soil,  subsoil,  streets, 
density  and  character  of  population,  dwellings,  yards,  closets, 
cesspools,  vaults,  drains,  conditions  of  cleanhness  and  atmos- 
pheric conditions,  revealed  nothing  of  interest.  But  a  study 
of  the  water  supply  discovered  most  interesting  facts.  Nearly 
all  of  the  cases  were  nearer  a  certain  public  pump  in  Broad 
Street  than  any  other  well,  and  most  of  them  gave  a  definite 
history  of  getting  water  from  this  pump.  Of  the  very  few 
cases  (ten  at  the  time  of  the  investigation)  outside  of  the 
area  supplied  by  this  pump,  half  were  known  to  drink  water 
from  Broad  Street.  There  were  also  several  cases  of  cholera 
in  distant  parts  of  London  in  persons  who  drank  water  from 
this  well.  In  the  workhouse  with  535  inmates,  in  the  midst 
of  this  district,  but  with  its  own  well,  there  were  only  5 
deaths,  less  than  one-tenth  the  rate  in  the  neighborhood,  and 

1  Sedgwick,   The    Principles  of    Sanitary  Science  and   the  Public 
Health,  New  York,  1902,  170. 

310 


INFECTION  BY  FOOD  AND  DRINK  317 

in  a  brewery  with  70  employees  and  using  its  own  well  there 
was  not  a  single  case.  It  was  also  shown  that  a  privy  vault 
and  cesspool  in  the  adjoining  house  discharged  through  a  leaky 
drain  which  ran  within  two  feet  of  the  well.  There  were  4 
fatal  cases  of  cholera  in  this  house  at  the  time  of  the  outbreak 
and  obscure  earlier  cases  which  were  not  unlikely  cholera 
also. 

North  Boston  Well.  —  In  the  United  States  the  outbreak 
of  typhoid  fever  at  North  Boston,  N.  Y.,  in  1843,  referred  to 
by  Flint  in  his  popular  text-books,  did  much  to  call  attention 
to  drinking  water  as  a  factor  in  the  spread  of  disease.  A 
young  man  from  Massachusetts  went  to  the  hamlet  sick  with 
typhoid  fever,  and  died  there.  He  lodged  at  the  tavern  where 
there  was  a  well  of  water  used  by  6  of  the  neighboring  fam- 
ilies. One  near-by  family  and  2  distant  families  did  not 
use  the  water  and  had  no  illness.  In  the  other  families  which 
did  use  the  water  there  were  28  cases  with  10  deaths.^ 

Recent  Studies.  —  Such  striking  demonstration  in  a  few 
instances  of  the  spread  of  disease  through  the  medium  of 
drinking  water  led  to  unwarranted  generalization,  and  during 
the  last  half  of  the  nineteenth  century  it  was  the  common 
belief  of  health  officials  and  medical  men  that  infected  water 
was  the  chief  factor  in  the  causation  of  typhoid  fever  and 
cholera,  and  that  it  was  of  great  importance  in  malaria,  yellow 
fever,  dysentery,  diarrhea,  and  was  perhaps  of  moment  in  all 
the  "  zymotic  "  diseases.  The  discovery  of  the  specific  organ- 
isms of  these  diseases,  and  the  application  of  more  scientific 
methods  to  their  stud}^,  has  of  late  shown  that  water,  while 
a  factor  of  very  great  importance,  is  not  so  important  as  was 
at  one  time  supposed.  Let  us  consider  its  relation  to  specific 
diseases. 

Typhoid  Outbreaks.  —  For  dwellers  in  temperate  regions 

typhoid  fever  is  the  most  important  water-borne   disease. 

The  demands  of  modern  civilization  require  for  the  constantly 

increasing  urban  population    a   pipe-distributed   municipal 

1  Am.  Pub.  Health  Ass.  Rep.,  1873,  I,  167. 


318        THE  SOURCES  AND  MODES  OF  INFECTION 

supply  which  in  numerous  instances  must  be  taken  from 
streams  or  lakes  more  or  less  contaminated  with  sewage. 
The  plentiful  use  of  water  rendered  possible  by  a  municipal 
supply  produces  a  large  amount  of  sewage,  which  in  the  past 
has  usually  discharged  into  the  nearest  watercourse,  thus 
carrying  danger  to  any  other  community  which  might  become 
a  user  of  the  water.  From  what  is  known  of  the  life  history 
of  the  typhoid  bacillus  it  is  not  surprising  that  in  some  cities 
great  explosive  outbreaks  of  the  disease  have  been  caused  by 
a  temporary  pollution,  and  other  cities,  owing  to  continuous 
pollution  of  their  source  of  supply,  have  suffered  from  a  con- 
tinuous high  death  rate  from  this  disease.  The  former  class 
of  outbreaks,  while  in  the  aggregate  less  destructive,  are  most 
impressive  lessons  for  the  public  and  have  been  exceedingly 
instructive  to  the  epidemiologist.  The  demonstration  of  a 
water-borne  outbreak  depends  primarily  upon  statistics.  If 
there  is  an  excess  of  typhoid  fever  among  the  users  of  a  certain 
water  over  the  neighboring  population  living  under  the  same 
conditions  but  using  a  different  water,  and  if  other  sources, 
as  food  and  milk,  are  excluded,  the  outbreak  is  probably 
water-borne.  The  more  closely  the  users  and  non-users  of 
the  water  are  commingled,  and  the  greater  the  difference  in 
the  incidence  of  the  disease  upon  them,  the  more  certain  is  the 
demonstration.  During  the  outbreak  in  Scranton,  1906-07,^ 
there  were  four  separate  sections  of  the  city  not  supplied 
from  the  infected  reservoir  in  which  there  was  very  little 
typhoid,  and  most  of  the  cases  which  did  occur  in  these  dis- 
tricts were  shown  to  have  used  the  infected  water  in  other 
places,  or  to  have  been  subject  to  contact  infection.  In 
Paris,^  owing  to  partial  failure  of  the  good  supply,  the  im- 
pure Seine  water  was  turned  on  to  one  arrondissement  after 
another,  with  the  result  that  a  well-defined  epidemic  followed 
in  each  instance.  In  Philadelpliia  the  gradual  introduc- 
tion of  filtered  water  has  resulted  in  a  decrease  in  typhoid 

1  Wainwrifrht,  N.  York  M.  J.,  1907,  LXXXV,  1027. 
«  Jonion,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  1669. 


INFECTION  BY  FOOD  AND  DRINK  319 

fever,  limited  to  those  districts  to  which  the  water  has  been 
suppHed. 

These  water-borne  outbreaks  are  usually  explosive  in  char- 
acter and  are  frequently  of  short  duration.  An  inspection  of 
the  supply  not  rarely  shows  that  the  feces  of  typhoid  cases 
have  entered  the  water  shortly  before  the  outbreak.  Such 
outbreaks  are  apt  to  occur  in  the  spring  when  the  freshets 
wash  the  surface  of  the  ground  into  the  streams.  The  bacilli 
have  rarely  been  found  in  tlie  incriminated  water. 

While  studying  this  subject  in  1888/  I  was  able  to  find 
thirteen  recorded  instances  of  the  recovery  of  typhoid  bacilli 
from  water  which  had  presumably  been  the  cause  of  an  out- 
break of  the  disease.  In  the  outbreak  in  Providence  in  that 
year  Prudden  and  Ernst  reported  finding  the  bacilli  in  house 
filters.  Methods  of  identifying  the  bacillus  at  that  time  were, 
however,  not  entirely  satisfactory^  and  it  is  not  certain  that 
the  bacteria  isolated  were  really  typhoid  bacilli.  By  better 
methods  the  germs  have  since  been  occasionally  found  in 
infected  waters,^  but  as  might  be  expected,  it  is  more  often 
from  wells  than  from  rivers  or  lakes.  According  to  Got- 
schlich,^  typhoid-fever  germs  have  been  identified  in  drinking 
water  by  the  agglutination  test  only  four  times.  Since  then, 
however,  they  have  been  isolated  by  Wesbrook*  from  the 
Mississippi  water  at  IVIinneapolis,  and  by  Fox  from  the  reser- 
voir which  was  the  source  of  the  Scranton  outbreak.^  The 
bacillus  isolated  by  Wesbrook  was  used  for  years  as  a  test 
organism  in  his  laboratory  and  also  by  Harris  at  Johns  Hop- 
kins. Anderson  and  Hutchings  and  Wheeler,  as  will  be  re- 
ferred to,  determined  the  presence  of  typhoid  bacilli  in  ice 
presumed  to  be  the  cause  of  the  disease. 

1  Chapin,  Boston  M.  &  S.  J.,  1889,  CXX,  604. 

2  J.  Mass.  Ass.  Bds.  Health,  Host.,  1904,  XIV,  66. 

'  Gotschlich,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1903, 
I,  191. 

*■  Wesbrook,  Brit.  M.  J.,  1897,  II,  1774. 
«  Rep.  St.  Bd.  Health,  Penn.,  1907,  410. 


320        THE  SOURCES  AND  MODES  OF  INFECTION 

Temporary  Typhoid  Infection.  —  These  explosive  and  tem- 
porary outbreaks  of  typhoid  fever  among  the  users  of  muni- 
cipal supplies  are  sometimes  due  to  an  accidental  pollution 
with  sewage,  but  are  more  often  due  to  the  overflow  of  privies, 
or  the  placing  of  the  discharges  of  typhoid  patients  on  the 
ground  where  they  can  be  washed  into  the  streams.  In  our 
lake  cities  they  have  sometimes  resulted  from  the  wind  tem- 
porarily blowing  the  sewage  of  the  city  towards  the  intake  of 
the  waterworks,^  or  the  dumping  of  dredged  mud  near  the 
intake."  Outbreaks  are  sometimes  due  to  the  careless  tem- 
porary use  of  polluted  water,  owing  to  failure  of  the  good 
supply,  as  at  Newburyport,^  or  the  accidental  sucking  in  of 
polluted  water  owing  to  some  derangement  of  valves  or  other 
mechanism,  as  in  Lowell,^  Baraboo  and  Millinocket.^ 

Continuous  Typhoid  Infection.  —  When  considerable 
amounts  of  sewage  are  discharged  into  a  stream  or  lake,  the 
water,  owing  to  the  prevalence  of  typhoid  fever,  must  be 
continuously  charged  with  the  bacilli.  The  users  of  the 
water  under  such  circumstances  generally  suffer  from  a  con- 
tinuously high  death  rate  from  this  disease.  Among  cities 
which  have  >so  suffered  may  be  mentioned  Chicago,  Pitts- 
burg, Cincinnati,  St.  Louis,  Philadelphia,  Newark  and  Al- 
bany. The  unenviable  position  of  many  Pennsylvania  cities 
in  this  respect  is  well  set  forth  by  Morris.**  Among  Euro- 
pean (;ities  which  have  had  a  l)ad  water  supply  are  Berlin, 
Hamburg,  Paris,  Frankfurt,  Altona,  Breslau  and  Zurich. 
Under  these  circumstances  the  typhoid  rate  may,  while  re- 
maining high,  vary  consideral)ly.  Sometimes  the  incidence 
of  the  disease  may  reach  enormous  proportions,  as  in  Chicago 

1  Whipple,  Typhoid  Fever,  New  York,  1908,  167-168. 

2  Whipple,  Typhoid  Fever,  New  York,  1908,  167;  also  U.  S.  Geol. 
Survey,  Wash.,  Water  Supply  and  Irrigation  Papers,  No.  194,  138. 

'  Rep.  St.  Bd.  Health,  Mass.,  1892,  701. 

*  Whipple,  Typhoid  Fever,  New  York,  1908,  174. 

*  Whipple,  Typhoid  Fever,  New  York,  1908,  178-179. 
"  Morris,  Sanitation,  Phila.,  August,  1904,  47. 


INFECTION  BY  FOOD  AND  DRINK  321 

in  1891,  when  it  was  173.8  per  100,000,  and  in  Pittsburg  in 
1900,  when  it  was  144.2.  Sometimes  epidemic  waves  of  the 
disease  can  be  followed  down  a  river  from  one  municipality 
to  another,  as  in  the  Merrimac,  Kennebec  and  Hudson.^ 

Cities  with  Infected  Water.  —  The  connection  between  an 
excessive  typhoid  death  rate  and  the  sewage  contamination 
of  municipal  water  supplies  is  thus  shown  by  a  large  amount 
of  epidemiological  evidence,  but  it  is  even  more  certainly  dem- 
onstrated by  the  improvement  which  almost  always  follows 
when  a  pure  water  is  substituted  for  the  impure.  Formerly 
typhoid  fever  was  very  common  in  English  cities,  but  now 
the  disease  is  far  less  prevalent,  due  in  large  measure  to  the 
almost  universal  use  of  clean  water.  Many  continental  cities 
present  marked  illustrations  of  the  decrease  in  typhoid  fever, 
due  to  improvement  in  water  supply.  Among  such  may  be 
mentioned  Paris,  Berlin,  Altona,  Hamburg,  Zurich,  Breslau 
and  Frankfurt.  The  United  States  also  presents  numerous 
examples,  as  Lawrence,  Lowell,  Albany,  Buffalo,  Newark, 
Jersey  City,  Cleveland,  Chicago  and  Philadelphia.  (For  more 
detailed  information  see  Whipple,  "Typhoid  Fever;"  Fuertes, 
"Water  and  Public  Health;"  Hazen,  "The  Filtration  of  PubUc 
Water  Supplies;"  and  Hazen,  "Pure  Water  and  How  to  Get 
It.")  It  has  in  one  or  two  instances  happened  that  the  purifi- 
cation of  a  polluted  water  supply  has  not  resulted  in  any  very 
marked  diminution  in  the  typhoid  death  rate.  This  was  so 
at  Youngstown,  Ohio,  and  notably  at  Washington.^  At 
Youngstown  the  disease  was  shown  to  be  spread  chiefly  by 
contact,  or  by  the  use  of  infected  wells.  The  conditions  at 
Washington  are  not  so  well  understood,  and  a  special  com- 
mission ^  has  been  able  to  find  no  very  definite  cause  for 
the  disease.     Levy  and  Freeman*  after  a  very  careful  study 

^  Whipple,  Typhoid  Fever,  New  York,  1908,  149,  154,  236. 
2  Whipple,  Typhoid  Fever,  New  York,  1908,  248. 
'  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Hyg.  Lab.,  Bull.  Nos.  35, 
44  and  51. 

*  Levy  and  Freeman,  Old  Dominion  J.  M.  &  S.,  1908,  VII,  315. 


322        THE  SOURCES  AND  MODES  OF  INFECTION 

of  conditions  in  Washington  and  Richmond,  conclude  ;;hat 
Washington  must  be  put  in  the  category  of  southern  cities 
in  which  an  excessive  typhoid-fever  rate  depends  chiefij^  on 
cHmatic  conditions  operating  more  or  less  directly,  and  that 
perhaps  to  a  considerable  extent  the  disease  depends  on  the 
presence  of  flies.  However  that  may  be,  Washington  affords 
a  practically  unique  example  among  large  cities  of  a  mistake 
in  attributing  the  excess  of  typhoid  fever  to  the  pollution  of 
the  water  supply. 

Amount  of  Sickness  Due  to  Water.  —  To  how  great  an 
extent  pollution  of  public  water  supplies  is  responsible  for  the 
excessive  typhoid  mortality  in  the  United  States  it  is  difficult 
to  determine.  Whipple^  says  that  the  average  typhoid  death 
rate  in  American  cities  is  about  35  per  100,000,  while  cities 
with  a  good  water  supply  average  not  over  20.  He  would 
thus  attribute  to  the  pollution  of  public  water  supplies  about 
40  per  cent  of  the  typhoid  fever  of  the  cities  of  the  United 
States.  We  must  remember,  however,  that  an  excess  of 
typhoid  fever  in  a  city  with  a  questionable  water  supply  is 
not  always  due  to  the  water,  as  witness  Washington  and 
Youngstown,  and  Dr.  H.  W.  Hill  writes  me  that  Duluth  is 
another  example.  But  a  majority  of  the  people  of  this  coun- 
try live  beyond  the  reach  of  municipal  water  supplies,  and 
typhoid  fever  is  even  more  prevalent  among  this  rural  popu- 
lation. So  that  if  the  whole  country  is  considered,  it  appears 
that  10  or  15  per  cent,  rather  than  40  ])er  cent,  of  our  typhoid 
fever  is  the  proper  proportion  to  attribute  to  the  infection  of 
municipal  supplies. 

Amount  Due  to  Wells.  —  Doubtless  the  majority  of  the 
inhabitants  of  the  United  States  obtain  their  drinking  water 
from  w(>lls.  Formerly  polluted  wells  were  believed  to  be  the 
chief  s(;ur('e  of  typhoid  fever.  This  was  particularly  so  while 
Murchison's  "pythogenic"  theory  of  the  origin  of  the  disease 
pn^vailed.  When  wells  were  a  principal  source  of  supply  in 
cities  where  ])rivy  vaults  and  cessjxjols  a])ound(Hl,  probably 
»  Whipple,  1  yphoid  Fever,  New  York,  1908,  132. 


INFECTION  BY  FOOD  AND  DRINK  323 

they  were  often  the  source  of  typhoid  fever.  With  the  sub- 
stitution of  municipal  pipe-supphes,  the  well  has  become  a 
factor  of  comparatively  little  moment  in  city  typhoid  fever. 
As  it  now  appears  that  the  bacillus  of  this  disease  does  not 
survive  long  in  soil  or  water,  and  that  each  case  must  have 
some  connection  with  a  previous  case  of  human  typhoid 
infection,  it  seems  improbable  that  country  wells,  largely  iso- 
lated as  they  must  be  from  danger  of  indiscriminate  human 
contamination,  play  an  important  part  in  the  propagation  of 
the  disease.  This  is  the  view  held  by  Hill,  who  has  had  a 
large  experience  in  the  study  of  this  disease  in  Minnesota. 
He  states,  however,  that  sometimes  in  loose  coarse  gravel, 
or  in  seamy  shale  and  limestone  formations,  wells  may  become 
infected  from  sources  of  pollution  situated  at  long  distances, 
and  have  then  been  known  to  be  the  cause  of  much  sickness. 
Instances  of  Infected  Wells.  —  That  wells  have  actually 
been  the  source  of  typhoid  fever  there  is  much  evidence. 
Instances  of  outbreaks  due  to  infected  wells  at  Basingstoke, 
England,  Newport,  R.  I.,  and  Trenton  are  narrated  by  Whip- 
ple,' and  a  dozen  or  more  instances  in  England  are  referred  to 
by  Poore,^  and  some  of  the  179  milk  outbreaks  of  typhoid 
fever  tabulated  in  "  Milk  and  Its  Relation  to  the  Public 
Health"^  were  due  to  infection  of  the  milk  by  water  from  a 
contaminated  well.  Outbreaks  due  to  well  water  continue 
to  be  reported  from  time  to  time.  During  twenty-five  years 
no  instance  of  typhoid  fever  from  infected  well  water  has 
come  under  my  personal  notice  except  at  a  summer  hotel  on 
the  shore  of  the  bay,  in  which  case  the  well  was  probably 
infected  by  a  broken  drainpipe  near  by.  An  interesting  case 
was  noted  in  Washington  a  few  years  since.^  Typhoid  fever 
occurred  in  four  houses  on  a  certain  street,  all  supplied  from 

1  Whipple,  Typhoid  Fever,  New  York,"  1908,  183-188. 
^  Poore,  The  Earth  in  Relation  to  the  Preservation  and  Destruc- 
tion of  Bacteria,  Lond.,  1902,  135. 

'  U.S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Hyg.  Lab.  Bull.  No.  41,  50. 
*  District  of  Columbia,  Report  of  Health  Officer,  1903,  29. 


324         THE  SOURCES  AND  MODES  OF  INFECTION 

wells.  A  little  further  up  the  street  there  had  previously 
been  some  cases,  the  feces  from  which  had  been  thrown  into 
a  privy  box  after  what  was  probably  only  partial  disinfection 
with  carbolic  acid.  At  any  rate  carbolic  acid  could  be  tasted 
in  the  water  in  the  wells  below.  While  in  this  instance  the 
infecting  material  probably  percolated  through  the  soil,  as 
it  did  also  in  the  outbreak  at  Trenton,  Whipple  states:' 
"  Sandy  soil  is  a  good  filtering  material,  and  when  a  well  in 
such  soil  stands  at  the  center  of  a  circle  twenty-five  or  fifty 
feet  in  radius  in  which  there  are  no  privies,  cesspools,  sink 
wastes,  or  other  sources  of  contamination,  the  water  can 
usually  be  depended  upon  as  fit  for  domestic  use, — provided, 
of  course,  that  the  top  of  the  well  is  properly  guarded  against 
surface  wash."  Sometimes,  as  in  the  Trenton  incident,  the 
infecting  material  passes  a  considerable  distance  apparently 
through  channels  or  crevices.  The  writer  once  knew  of  a  well 
which  became  polluted  (though  without  causing  sickness) 
from  a  privy  300  feet  distant,  after  there  had  been  much 
blasting  near  by,  which  presumably  opened  seams  in  the 
somewhat  slaty  rock.  As  Whipple  says,  most  wells  which 
have  been  the  cause  of  typhoid  outbreaks  have  been  contam- 
inated from  the  top. 

Infected  Springs.  —  Springs  are  essentially  natural  wells,, 
and  there  is  no  reason  why  they  should  not  occasionally  be 
contaminated.  A  typhoid  outbreak  caused  by  spring  water 
occurred  at  Mount  Savage,  Md.,  in  1904,^  another  at  Spring- 
field, Mass.,^  one  at  Northampton,  Mass.,^  one  at  Ridgway, 
Penn.,^  and  two  others  in  Maryland." 

Typhoid  Fever  from  Bathing.  —  It  has  been  suggested 
from  time  to  time  that  typhoid  fever  may  result  from  bathing 

'  WhiF:)pIo,  Typhoid  Fever,  New  York,  1908,  85. 

»  Whipple,  Typhoid  Fever,  New  York,  1908,  188. 

'  Kep.  Bd.  Health,  Spriiiirfield,  1903,  IG. 

«  Rep.  St.  lid.  Health,  Ma.s.s.,  1900,  844. 

<•  Rep.  St.  IM.  Health,  Penn.,  1907,  927. 

•  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  595. 


INFECTION  BY  FOOD  AND  DRINK  325 

in  water  containing  typhoid  bacilli,  the  infection  presumably 
being  due  to  the  accidental  swallowing  of  some  of  the  water. 
Reece  ^  has  recently  reported  an  outbreak,  presumably  due 
to  this  cause,  at  the  naval  recruiting  station  at  Walmer.  The 
swimming  tank  was  infected  with  sewage  containing  typhoid 
excreta,  and  the  earlier  cases  seemed  to  be  closely  connected 
with  the  use  of  the  tank.  From  the  report,  however,  it  does 
not  appear  that  contact  infection  outside  the  tank  could  be 
rigidly  excluded. 

Cholera  from  Water.  —  Cholera  was  early  shown  to  be 
a  water-borne  disease.  The  longevity  of  the  spirillum  in 
water  is  probably  not  so  great  as  that  of  the  typhoid  bacillus, 
but  it  is  sufficient  to  permit  of  the  disease  being  easily  trans- 
mitted in  this  manner.  Whenever  the  excreta  of  human 
beings  infected  with  cholera  gain  access  to  cisterns,  wells, 
streams  or  other  sources  of  drinking  water,  cholera  is  pretty  sure 
to  follow.  The  cholera-infected  Broad  Street  well  in  London 
has  been  referred  to,  and  although  for  many  years  the  views 
of  health  officials  were  somewhat  colored  by  the  miasm  theory 
of  Pettenkofer,  the  transmission  of  the  disease  by  water  was 
kept  in  mind,  and  many  outbreaks  due  to  this  cause  were 
reported.  Radcliffe,  Simon  and  others  ^  showed  that  infected 
water  played  a  large  part  in  the  outbreaks  of  cholera  in  Lon- 
don in  1848-49,  1853-54  and  1866.  Shakespeare  in  his  very 
valuable  Report  on  Cholera  in  Europe  and  India^  gives  nu- 
merous instances  of  water-borne  cholera  infection,  as  from 
wells  at  several  places  in  France  (pp.  76-81) ,  and  from  muni- 
cipal supplies  in  Genoa  and  Naples  (p.  151).  In  Spain  many 
towns  and  villages  suffered  from  water-borne  outbreaks, 
caused  often,  doubtless,  by  the  universal  custom  of  washing 
soiled  linen  in  running  streams.  According  to  Shakespeare, 
water  plays  an  important  part  in  the  spread  of  cholera  in 

'  Rep.  Med.  Off.  Loe.  Gov.  Bd.,  1908-09,  XXXVIII,  90. 
^  Sedgwick,  Principles  of  Sanitary  Science  and  the  Public  Health, 
New  York,  1902,  182. 

3  U.  S.  Government  Printing  Office,  1890. 


326        THE  SOURCES  AND   MODES  OF  INFECTION 

India,  and  Koch^  reported  finding  the  spirilla  in  a  tank  used 
as  a  village  water  supply.  A  number  of  instances  of  the 
finding  of  cholera  spirilla  in  water  that  was  presumably  the 
cause  of  the  disease  are  noted  by  Kolle.^  Cases  are  recorded 
of  explosive  outbreaks  of  cholera  on  shipboard,  probably  due 
to  infected  water.^  The  most  striking  instance  of  the  trans- 
mission of  cholera  by  water  is  the  celebrated  outbreak  in 
Hamburg  and  Altona  in  1892.  These  two  municipalities 
form  practically  one  city,  though  each  has  its  own  water 
supply.  In  the  outbreak  Hamburg,  which  used  unfiltered 
and  polluted  Elbe  water,  suffered  severely,  while  Altona,  the 
water  for  which  was  filtered,  was  almost  exempt.  The  line  of 
demarcation  between  the  two  water  supplies  could  be  recog- 
nized by  the  incidence  of  the  disease.  Our  officers  in  the 
Philippines  attribute  great  importance  to  water  as  a  vehicle 
for  the  diffusion  of  cholera,  particularly  in  the  villages  and 
smaller  towns,  where  the  streams  are  used  for  washing  clothes 
and  for  sewers  and  at  the  same  time  as  sources  of  domestic 
supply.  The  municipal  supply  of  Manila  has  been  kept  free 
from  infection  during  the  last  outbreaks,  though  wells  have 
to  some  extent  been  the  cause  of  sickness.  Woodruff*  states 
that  in  one  town  a  spring  supplied  part  of  the  people,  who 
were  quite  free  from  the  disease,  which  nearly  decimated  those 
using  the  river,  and  in  those  towns  where  the  people  had  well- 
protected  rain-water  cisterns  they  were  quite  immune.  While 
we  are  not  in  a  position  to  determine  the  relative  importance 
of  water  in  the  causation  of  cholera,  it  appears  certain  that  it 
is  a  factor  of  great  consequence,  and  that  people  using  a 
sewage-polluted  water  are,  on  the  advent  of  cholera,  liable  to 
suffer  from  severe  epidemics  of  the  disease. 

Dysentery  from  Water. — The  l)a('illus  of  dysentery  is  found 
in  the  discharges  from  the  bowels,  and  has  about  the  same 

1  Koch,  Brit.  M.  J.,  Lond.,  1884,  II,  403,  453. 

"  Kollc  u.  Wassermann,  Handbuch  [etc.],  Jena,  I,  191;  III,  61. 

3  Wcndt,  Awiatic  Cholera,  New  York,  188.5,  113. 

<  Woodruff,  J.  Am.  M.  Ass.,  1905,  XLV,  1100. 


INFECTION  BY  FOOD  AND  DRINK  327 

resistance  as  the  typhoid  bacillus,  so  that  we  should  expect 
this  form  of  dysentery  to  spread  in  much  the  same  way  as 
typhoid  fever  does,  and  that  infected  water  would  prove  a 
factor  of  importance.  Shiga^  reports  outbreaks  in  Japan  from 
the  use  of  well  and  river  water.  Eldridge^  states  that  dysen- 
tery is  a  rural  disease  in  Japan,  and  the  use  of  human  feces 
as  a  fertilizer,  and  the  frequency  of  the  infection  of  the  nu- 
merous small  streams  and  wells,  renders  it  preeminently  a 
water-borne  disease. 

Little  is  heard  about  water-borne  outbreaks  of  dysentery 
in  England  or  the  eastern  United  States,  and  it  is  highly 
probable  that  such  are  not  very  common.  Dr.  H.  W.  Hill 
reports  four  such  outbreaks  in  Minnesota,  three  of  which 
are  briefly  referred  to  in'  the  report  of  the  Minnesota  state 
board  of  health  for  1911.  At  Hibbing  in  1907  about  2000 
out  of  8000  persons  were  attacked,  although  only  5  deaths 
occurred.  The  infection  was  probably  caused  by  work- 
men going  down  into  the  well  to  make  repairs.  After  the 
institution  of  the  hypochlorite  treatment  of  the  water  the 
outbreak  abruptly  ceased.  At  St.  Peter  there  were  out- 
breaks in  1908  and  in  1909.  Both  were  due  to  a  polluted 
river  water  overflowing  into  a  reservoir.  At  the  Agri- 
cultural College  a  deep  well  was  infected  by  the  backing  up 
of  a  sewer,  and  almost  every  person  who  drank  the  water 
developed  dysentery.  At  Mankato,  Minn.,  there  was  an 
outbreak  of  405  cases  of  typhoid  fever  due  to  sewage  leak- 
ing into  the  well  which  supplied  the  town.  Preceding  the 
typhoid  cases  there  were  4000  to  6000  cases  of  diarrhea 
and  dysentery,  nearly  half  the  population,  the  first  cases 
appearing  June  25,  immediately  after  the  infection  of  the 
water  and  lasting  until  early  in  July.^ 

There  is  every  reason  to  believe  that  dysentery  amebaB 

»  Shiga,  Mod.  Med.  [Osier],  Phila.  &  N.  Y.,  1907,  II,  781. 

2  Eldridge,  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Pub.  Health 
Rep.,  1900,  1. 

3  J.  Infect.  Dis.,  Chicago,  1911,  IX,  410. 


328       THE  SOURCES  AND  MODES  OF  INFECTION 

are  carried  in  water.  Musgrave  and  Clegg^  claim  to  have 
found  the  amebse  in  the  water  supply  of  Manila,  but  there 
is  some  doubt  as  to  the  pathogenicity  of  the  forms  studied 
by  them.  Allan-  reported  a  small  outbreak  of  amebic 
dysentery  in  North  Carolina,  due  to  an  infected  well. 

Diarrhea  from  Water.  —  Reincke^  states  that  infantile 
diarrhea  was  greatly  lessened  after  the  improvement  in  the 
water  supply  of  Hamburg.  Sir  Shirley  F.  Murphy,  Seaton 
and  Newsholme  in  the  discussion  of  the  paper  took  issue 
with  its  writer  as  to  the  part  played  by  water  in  the  causa- 
tion of  this  disease.  Sedgwick^  says  that  there  is  no  doubt 
that  drinking  water  is  the  ready  vehicle  of  dysentery  and 
diarrhea.  He  refers  to  the  Ninth  Report  of  the  Medical 
Officer  of  the  Privy  Council,  London,  1867,  p.  16,  and  to 
his  own  investigations  as  to  the  excessive  prevalence  of 
typhoid  fever  and  diarrhea  in  Burlington  owing  to  the 
sewage  contamination  of  the  water  supply.^  Sedgwick 
also,  in  the  paper  mentioned  on  another  page,  quotes 
freely  from  Reincke's  various  writings  to  show  that  well- 
defined  outbreaks  of  diarrheal  disease  have  occurred  in 
Altona,  Hamburg  and  Berlin  in  connection  with  defective 
working  of  the  filters  or  with  unusual  pollution  of  the  water 
sui^ply  due  to  other  causes. 

Water  in  Relation  to  Seasonal  Distribution  of  Diarrhea. — 
In  an  article  just  publishetl,  McLaughlin^  attributes  very 
considerable  importance  to  water  suiiplies  in  the  causation 
of  infantile  diarrheas.  He  recognizes  the  fact  that  these 
diarrheas  may  include  at  times  nmch  typhoid  fever  and 
much  dysentery,  and  jK^-haps  other  varieties  of  intestinal 

'  liuU.  IS,  Bu.  Gov.  Lab.,  P.  L,  93;  Rep.  Bd.  Health,  P.  I.,  1904-5, 10. 

-  Allan,  J.  Am.  M.  Ass.,  Cliicago,  1909,  LIII,  1561. 

^  Reincke,  Trans.  Epidenuol.  Soc,  Lond.,  1904,  n.  s.,  XXIII,  135. 

■•  Sedgwick,  Principles  of  Sanitary  Science  and  the  Public  Health, 
New  York,  1902,  217. 

'  J.  N.  Eng.  Water  Works  Ass.,  X,  1()7. 

«  Pub.  Health  Rep.,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Wash., 
1912,  XXVII,  579. 


INFECTION  BY  FOOD  AND  DRINK  329 

infection.  He  also  admits  that  many  factors  other  than 
the  water  supply  are  often  of  far  more  importance  than  is 
the  water.  He  bases  his  contention  as  to  the  danger  from 
water  on  an  excessive  prevalence  of  diarrheal  diseases  in  the 
winter  months,  alleging  that  while  ignorance,  poverty  and 
"  unsanitary  conditions  "  may  cause  an  enormous  excess 
in  summer,  in  towns  with  pure  water,  they  do  not  cause  such 
an  excess  in  the  winter.  He  gives  some  striking  illustra- 
tions of  communities  with  a  grossly  polluted  water  supply 
which  have  an  excess  of  winter  diarrhea  as  well  as  of  winter 
typhoid  fever.  Among  these  may  be  mentioned  Niagara 
Falls  and  Cohoes,  N.  Y.,  and  Escanaba  and  Marquette, 
Mich.  The  evidence  from  the  larger  cities  of  Cleveland, 
Chicago,  Milwaukee  and  Pittsburg  is  not  so  convincing.  It 
is  true  that  these  do  show  a  very  considerable  excess  of  win- 
ter diarrhea  and  that  the  curves  for  the  three  lake  cities  are 
strikingly  parallel,  but  if  this  winter  diarrhea  is  really  the 
result  of  and  proof  of  dangerous  pollution  of  the  water  we 
should  expect  a  correspondingly  great  excess  of  typhoid 
fever  in  these  cities;  yet  the  typhoid  death  rate  in  all  of 
them  is  below  the  average.  Indeed  there  is  no  very  marked 
parallelism  between  typhoid  fever  and  diarrhea  either  in 
different  cities  or  in  the  same  city  at  different  seasons.  In 
some  of  McLaughlin's  tables  the  curves  of  winter  diarrhea 
and  winter  typhoid  fever  correspond  exactly  and  in  others 
they  are  months  apart.  While  on  guard  not  to  attribute 
too  much  importance  to  water  as  a  source  of  diarrhea  we 
must  admit  that  McLaughlin  has  presented  new  evidence  to 
show  that  water  is  at  times  a  factor  to  be  reckoned  with. 
The  Mills-Reincke  Phenomenon.  —  In  1893  Mills  of 
Lawrence,  Mass.,  and  Reincke  of  Hamburg,  Germany, 
noted  that  the  purification  of  the  water  supplies  of  their 
respective  towns  was  followed  by  a  decrease  in  the  general 
death  rate  as  well  as  in  the  death  rate  from  typhoid  fever. 
Hazen  later  called  attention  to  these  facts,  which  he  found  to 
hold  true  for  other  American  cities,  and  he  was  in  accord 


330        THE  SOURCES  AND  MODES  OF  INFECTION 

with  the  first-named  observers  in  attributing  the  decrease 
to  the  improvement  in  the  water  and  maintained  that 
where  one  death  from  typhoid  could  be  prevented  by  im- 
proving the  water  supply  two  or  three  deaths  from  other 
causes  would  be  prevented  by  the  improvement.  Sedg- 
wick and  McNutt/  in  an  elaborate  paper,  have  presented  a 
large  amount  of  material  which  they  believe  establishes  the 
fact  of  the  phenomenon  and  also  indicates  which  diseases 
are  chiefly  affected  by  the  water  supply.  The  authors 
consider  that  their  data  show  that  an  improvement  in  a 
poor  water  supply  may  be  expected  not  only  to  reduce  the 
death  rate  from  typhoid  fever  but  to  decrease  infant  mor- 
tality and  the  death  rate  from  gastro-intestinal  disturbance 
and  from  tuberculosis  and  pneumonia.  It  has  been  sug- 
gested that  these  changes  may  be  due  to  the  removal  of 
disease  germs  from  the  water,  or  to  increased  bodily  re- 
sistance due  to  better  water,  or  to  both.  As  to  the  explana- 
tion, however,  Sedgwick  and  McNutt  offer  no  opinion. 

Water  Purification  and  the  General  Death  Rate.  — 
According  to  the  theory  under  discussion  the  purification 
of  a  polluted  water  supply  causes  a  fall  in  the  general  death 
rate  below  that  due  to  the  diminution  of  typhoid  fever. 
This  decrease  certainly  took  place  in  Lawrence  and  Lowell, 
but  the  deaths  in  a  city  during  a  year  are  due  to  a  great 
number  of  diseases,  and  the  prevalence  of  each  disease  and 
each  death  from  that  disease  are  due  to  the  joint  action  of 
very  many  causes.  To  attribute  a  change  in  the  death 
rate  to  any  one  cause  is  extremely  dangerous  and  in  the  past 
has  led  to  most  serious  errors.  It  can  be  seen  from  the 
diagram  shown  by  Sedgwick  and  McNutt  that  in  both  the 
cities  under  consideration  there  had  been  a  considerable 
rise  in  the  death  rate  just  previous  to  changes  in  the  water 
supply  and  that  a  considerable  part  of  the  increase  was  due 
to  pneumonia  as  was  also  a  considerable  part  of  the  de- 
crease.    Changes  equally  as  great  in  the  mortality  from 

1  Sedgwick  and  McNutt,  J.  Infect.  Dis.,  Chicago,  1910,  VII,  489. 


INFECTION  BY  FOOD  AND  DRINK  331 

pneumonia  and  in  the  general  death  rate  have  occurred  in 
Albany,  as  shown  in  Sedgwick  and  McNutt's  diagram,  and 
doubtless  in  other  cities,  entirely  independent  of  changes  in 
the  water  supply,  and  such  changes  may  as  well  be  assumed 
to  be  due  to  variation  in  the  prevalence  of  influenza  or  to 
some  other  cause  as  to  changes  in  the  water  supply.  That 
two  cities  close  together  had  a  decrease  in  the  death  rate,  in 
large  part  due  to  decrease  in  respiratory  diseases,  at  the 
same  time  that  the  water  supply  was  changed  might  well 
be  due  to  chance.  It  is  suggestive  that  the  change  was 
most  marked  in  the  two  cities  in  the  same  year  although 
the  water  in  Lowell  was  only  partially  improved  in  that 
year.  It  may  also  be  noted  that  the  decline  in  the  death 
rate  in  Albany  started  from  a  maximum  in  1892,  the  year 
before  the  maximum  in  the  Massachusetts  cities,  and  that 
this  maximum  coincided,  as  in  Massachusetts,  with  a  maxi- 
mum mortality  from  respiratory  diseases.  The  rate  of 
decrease  in  total  mortality  and  in  respiratory  mortality  was 
not  as  great  after  filtration  as  before,  and  it  was  about  as 
great  as  the  decline  in  Lawrence  and  Lowell  which  was 
supposed  to  be  due  to  water. 

Water  Purification  and  Diarrhea.  —  The  infant  death 
rate,  in  which  the  diarrheal  diseases  play  an  important  part, 
has  been  shown  to  have  the  closest  sort  of  relation  to  kinds 
of  food  and  methods  of  feeding  and  to  vary  enormously  in 
different  sections  of  the  same  city  and  among  different 
classes  residing  in  the  same  section.  A  body  of  statistics, 
far  more  voluminous  than  are  marshalled  in  support  of  the 
Mills-Reincke  theory,  indicates  that  very  great  reduction 
can  readily  be  made  in  the  infant  death  rate  by  better 
feeding  and  other  care.  Yet  we  are  asked  to  believe  that 
the  diarrheal  deaths  in  Hamburg  were  cut  in  half  by  the 
change  in  the  water.  One  cannot  help  thinking  either 
that  the  old  water  supply  was  specifically  infected  with  the 
germs  of  diarrhea,  which  is  not  the  case  in  most  English  and 
American  cities,  or  else  that  the  changes  in  population  and 


332       THE  SOURCES  AND  MODES  OF  INFECTION 

in  sanitation,  after  the  great  cholera  outbreak,  produced  in 
themselves  great  changes  in  the  diarrheal  death  rate. 
Indeed,  the  writer  has  been  informed  by  a  well-known 
scientific  man,  then  residing  in  Hamburg,  that  the  cholera 
outbreak,  by  its  destruction  of  life,  and  consequent  changes 
in  the  population,  profoundly  modified  mortality  rates.  If 
we  turn  to  Sedgwick  and  McNutt's  diagram  for.  Lawrence 
we  see  no  change  in  the  diarrheal  death  rate  between  the 
7  years  before  and  the  7  years  after  filtration.  In  Lowell 
the  diarrheal  death  rate  did  decline  decidedly  after  the  im- 
provement in  the  water.  In  Albany  the  decrease  began 
before  the  improvement  in  the  water  and  continued  at 
about  the  same  rate  afterwards.  ^ 

Water  Purification  and  Tuberculosis.  —  As  shown  by 
Sedgwick  and  McNutt,  pulmonary  tuberculosis  had  been 
declining  for  many  years  in  Lawrence  and  Lowell,  as  it  had 
in  most  cities,  and  the  diagrams  indicate  a  retarded  rather 
than  an  accelerated  decline  after  the  improvement  in  the 
water.  The  authors,  in  order  to  show  the  alleged  effect 
of  the  water  improvement,  are  obliged  to  compare  these 
cities  with  Manchester,  which  they  assume  differs  from 
Lowell  and  Lawrence  chiefly  in  having  a  good  water  supply, 
and  which  they  consider  a  "  normal  "  city  for  their  purpose. 
Compared  with  Manchester,  Lawrence  shows  a  greater  de- 
crease by  30  deaths  and  Lowell  by  68.  While  the  authors 
state  that  the  age,  sex,  occupation  and  nationality  of  the 
population  of  the  three  cities  is  substantially  the  same,  it 
would  appear  rather  risky  to  assume  that  all  the  conditions 
affecting  health  are  the  same.  Cities  show  great  variation 
as  regards  their  mortality,  even  when  the  figures  are  cor- 
rected for  age  and  sex,  and  would  doubtless  do  so  if  cor- 
rected for  nationality  and  occupation.  One  of  the  most 
difficult  problems  in  vital  statistics  is  to  make  correct 
deductions  from  a  (comparison  of  the  death  rate  of  different 
cities,  particularly  in  such  a  disease  as  tuberculosis.  A 
theorem  wliich  dejx'iids  upou  a  comparison  made  as  above 


INFECTION  BY  FOOD  AND  DRINK  333 

seems  to  require  further  study.  In  Albany  following  fil- 
tration there  was  no  apparent  change  in  the  steady  decrease 
in  tuberculosis  which  had  been  going  on  for  several  years. 
Notwithstanding  the  efforts  that  have  been  made  by  some 
to  show  by  statistics  that  the  dechne  in  tuberculosis  has 
been  due  to  sewerage,  and  by  others  that  it  is  dependent  on 
the  segregation  of  advanced  cases,  and  by  still  others  that 
it  is  the  result  of  the  recent  popular  propaganda,  and  now 
by  the  supporters  of  the  Mills-Reincke  theory  that  it  is 
dependent  in  a  very  appreciable  measure  on  improvement 
in  water  supplies,  I  cannot  see  that  the  evidence  presented 
along  any  of  these  lines  is  sufficient  to  warrant  official  action 
or  definite  predictions.  We  know  less  about  the  causation  of 
tuberculosis  than  about  almost  any  other  infectious  disease. 

Water  Purification  and  Pneumonia.  —  While  Sedgwick 
and  McNutt  say  with  reference  to  diphtheria  that  "  the 
mixed  character  of  the  title  and  the  highly  epidemic  char- 
acter "  of  the  disease  render  no  conclusions  possible,  they 
believe  that  valid  deductions  can  be  drawn  from  a  study  of 
pneumonia.  This  disease  group  has,  however,  during  the 
last  25  years,  shown  marked  epidemicity,  due,  I  believe,  in 
large  part,  to  the  effect  of  influenza.  There  was  in  New 
England  a  notable  increase  of  pneumonia  in  the  early 
nineties  followed  by  a  decline  and  then  another  increase  a 
few  years  later,  though  the  curves  have  varied  somewhat  in 
different  cities.  There  was  a  sudden  drop  in  pneumonia 
mortality  in  Lawrence  after  filtration  and  a  slight  increase 
in  Lowell,  but  for  the  reason  given  no  deduction  is  permis- 
sible as  to  the  influence  of  the  water. 

Results  of  PHirification  in  Providence.  —  An  excellent 
sand  filter  was  installed  in  Providence  in  January,  1906. 
There  was  an  appreciable  decrease  in  the  amount  of  typhoid 
fever  but  it  is  doubtful  if  it  was  dependent  on  filtration. 
There  was  not  very  much  change  in  the  general  death  rate 
in  Providence  following  filtration,  though  it  was  slightly 
higher  in  the  2  years  after  filtration  was  begun  than  it  was 


334        THE  SOURCES  AND  MODES  OF  INFECTION 

in  the  2  years  l^efore  filtration.  Tuberculosis,  which  had  been 
declining  for  many  years,  exhibited  a  somewhat  retarded 
decline  after  1906.  Pneumonia  after  1905  showed  a  decided 
increase  over  the  preceding  10  years,  though  there  was 
little  change  during  the  3  years  before  filtration  and  the 
2  years  after.  Diarrheal  diseases  had  been  declining  and 
reached  a  minimum  in  1905,  the  year  before  filtration,  fol- 
lowed by  a  considerable  increase  during  the  next  2  years. 
Certainly  there  is  nothing  in  these  figures  to  indicate  that 
an  improved  water  supply  has  caused  a  decrease  in  the 
diseases  mentioned. 

McLaughlin's  Evidence  concerning  Mills-Reincke  Phe- 
nomenon.—  McLaughlin^  has  also  given  consideration  to 
the  Mills-Reincke  theorem,  and,  as  does  the  present  writer, 
hesitates  to  make  deductions  from  such  a  complicated 
phenomenon  as  changes  in  the  general  death  rate.  He 
prefers  to  study  single  diseases,  and  considers,  in  the  paper 
cited,  infantile  diarrhea.  His  argument  as  to  the  effect  on 
the  diarrheal  death  rate  by  improving  the  water  supply  is 
based  on  the  causative  connection  between  water  and  diar- 
rhea which  he  seeks  to  establish  as  referred  to  above.  He 
also  gives  tables  of  deaths  in  four  cities  which  have  recently 
wholly  or  to  a  large  extent  changed  their  water  supplies, 
namely  Cincinnati,  Columbus,  Pittsburg  and  Philadelphia. 
All  have  shown  a  very  great  decrease  in  the  death  rate  from 
typhoid  fever.  In  Cincinnati  and  Columbus  there  was  no 
decrease  in  diarrhea;  in  Philadelphia  it  was  very  slight,  but 
in  Pittsburg  it  was  quite  noticeable.  This  maintenance 
of  the  diarrheal  death  rate  is  rather  remarkable  in  view  of 
the  direct  efforts  that  have  been  made  during  the  last  few 
years  to  decrease  infant  mortality.  The  figures  for  pneu- 
monia are  not  given  by  McLaughlin.  Tuberculosis  de- 
creased in  the  four  cities,  but  the  decrease  had  been  going 
on  for  some  time  as  in  most  cities. 

'  Pub.  Health  Rep.,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Wash., 
1912,  XXVLI,  597. 


INFECTION  BY  FOOD  AND  DRINK  335 

Conclusion  concerning  the  Theorem.  —  No  attempt  is 
here  made  to  disprove  tlie  reality  of  tlie  Mills-Reiiicke 
phenomenon  but  only  to  call  attention  to  certain  difficulties 
in  accepting  it.  It  is  a  question  of  great  importance  which 
ought  to  receive  extended  study.  A  number  of  important 
cities  have  recently  improved  their  water  supplies  with  a 
corresponding  decrease  in  typhoid  fever.  The  effect  upon 
other  diseases  should  be  carefully  examined.  At  present  it 
seems  unwise  to  consider  the  proposition  demonstrated  and 
to  promise  a  lowering  of  the  general  death  rate  as  a  result 
of  the  purification  of  water  supplies. 

Malaria  from  Water.  —  Until  recently  malaria  has  been 
believed  to  be  transmitted  by  means  of  drinking  water. 
Numerous  instances  were  reported,  such  as  that  of  the  ship 
Argo,  in  which  it  was  supposed  that  the  evidence  pointed 
conclusively  to  this  mode  of  transmission.  The  discovery 
of  the  part  played  by  the  mosquito  in  the  causation  of  this 
disease  led  to  a  more  critical  consideration  of  the  alleged 
evidence  in  support  of  its  water-borne  character,  and  most 
of  this  evidence  was  found  to  be  worthless,  or  in  the  few 
instances  in  which  water  still  seemed  to  be  at  fault  it  ap- 
peared probable  that  the  water  served  as  a  breeding  place 
for  mosquitoes,  and  did  not  directly  cause  disease  by  its 
ingestion. 

There  was  nothing  in  the  earlier  demonstrated  facts  of  the 
transmission  of  the  disease  by  insects  to  preclude  the  pos- 
sibility of  its  transmission  by  water,  and  indeed  Laveran  and 
Manson  thought  this  not  improbable.  Celli  ^  attempted  to 
demonstrate  this  in  various  ways  by  administering  water 
from  the  most  malarious  regions  of  Italy  to  human  beings, 
daily,  up  to  a  month.  He  failed  completely,  as,  according  to 
Craig,^  have  all  other  experimenters,  except  Ross  in  one  in- 
stance, which,  however,  from  the  conditions  of  the  experi- 
ment, was  far  from  conclusive.     Celli  considers  the  fact  that 

1  Celli,  Malaria,  Lond.,  1900,  94. 

2  Craig,  The  Malarial  Fevers,  New  York,  1909,  82. 


836       THE  SOURCES  AND  MODES  OF  INFECTION 

large  numbers  of  railway  employees  and  others  living  in 
intensely  malarious  regions  around  Rome  use  an  unques- 
tionably pure  aqueduct  water,  but  are  yet  frequently  at- 
tacked by  malaria,  is  corroborative  evidence  that  water 
cannot  be  an  important  vehicle  of  the  disease.  But  prob- 
ably the  best  evidence  we  have  that  drinking  water  plays  no 
part  in  the  causation  of  malaria  is  the  fact  that  preventive 
measures  all  over  the  world,  directed  solely  against  the 
mosquito  and  with  no  reference  to  the  water  theory,  have 
resulted  in  an  enormous  decrease  and  in  some  places  in  the 
eradication  of  the  disease. 

Yellow  Fever  from  Water.  —  Yellow  fever  also  was 
formerly  believed  to  be  at  times  water-borne,  but,  as  in 
malaria,  the  epidemiological  evidence  therefor  will  not  stand 
criticism.  The  success  of  the  preventive  measures  directed 
solely  against  the  mosquito  indicates  that  drinking  water 
has  no  part  in  the  diffusion  of  this  disease. 

Worms  in  Water.  —  The  eggs  and  young  of  some  of  the 
parasitic  worms  are  often  swallowed  in  drinking  water,  and 
the  Ankylostoma  and  Bilharzia,  and  others  probably,  enter 
the  skin  from  water  in  which  they  are  contained,  but  the 
consideration  of  the  diseases  caused  by  them  is  outside  the 
scope  of  this  essay. 

Conclusions.  —  Among  the  diseases  which  may  be  trans- 
mitted by  water,  typhoid  fever  is  doubtless  by  far  the  most 
important  in  Europe  and  North  America  at  the  present 
time.  When  water-borne  disease  is  mentioned,  typhoid 
fever  comes  first  to  mind.  Yet  there  are  those  who  think 
that  the  role  of  water  in  this  disease  has  been  exaggerated,^ 
and  it  is  doubtless  true  that  in  Europe,  and  even  in  this 
country,  recent  improvements  in  water  supplies  have  greatly 
diminished  this  disease,  but  there  are  still  a  great  many 
communities  drinking  polluted  water  and  having  a  con- 
sequently high  typhoid  death  rate.  It  is  probably  true 
that  other  fecal-borne  diseases  such  as  the  diarrheal  group 
1  Houston,  J.  State  M.  Loud.,  1912,  XX,  21,  92. 


INFECTION  BY  FOOD  AND  DRINK  337 

are  transmitted  through  the  medium  of  water.  Asiatic 
cholera  too  may  cause  great  devastation  through  infection 
of  water  suppHes,  but  for  a  number  of  years  the  western 
world  has  been  remarkably  free  from  this  disease.  Typhoid 
fever  is,  however,  such  a  common  and  serious  disease,  caus- 
ing probably  25,000  deaths  annually  in  the  United  States, 
as  well  as  an  enormous  amount  of  disability  at  the  most  use- 
ful period  of  life,  that  it  is  worth  while  to  make  large  expend- 
itures for  its  prevention.  Such  expenditures  are  to  be  still 
further  encouraged,  since  it  is  certain  that  the  means  taken 
to  prevent  the  diffusion  of  typhoid  fever  by  water  will  also 
prevent  the  spread  of  cholera  and  bacillary  dysentery. 

Protection  of  Water  Supplies.  —  In  the  three  diseases  just 
mentioned  the  sole  source  of  infection  of  water  is  the  excreta 
of  persons  infected  with  the  specific  germs.  If  these  excreta 
can  be  kept  out  of  drinking  water,  or  if  the  germs  can  be 
removed  from  it  after  it  is  infected,  the  problem  is  solved,  and 
this  can  be  done  at  a  not  prohibitive  expense.  For  a  full 
and  practical  consideration  of  the  means  for  obtaining  a  pure 
water  supply  reference  should  be  had  to  such  works  as  Hazen's 
"The  Filtration  of  Public  Water  Supplies"  and  "Pure  Water 
and  How  to  Get  It."  Suffice  it  to  say  here  that  pure  water 
may  be  obtained  by  securing  a  clean  source  or  by  adopting 
some  method  of  purification. 

Domestic  Wells.  —  The  larger  part  of  our  population  ob- 
tains its  drinking  water  from  shallow  wells,  and  it  is  usually 
neither  difficult  nor  expensive  so  to  locate  them  that  they 
will  not  receive  drainage  from  privies  or  sink  drains,  and  so 
to  protect  them  that  they  will  not  receive  surface  washings. 
The  federal  Department  of  Agriculture  and  the  state  and  local 
boards  of  health  should  do  and  are  doing  much  to  instruct 
farmers  and  villagers  concerning  the  location  and  protection 
of  wells. 

Municipal  Supplies.  —  As  regards  municipal  supplies  it  is 
desirable  if  possible  that  the  water  be  uncontaminated.  This 
may  be  secured  by  drawing  from  deep  wells,  or  seeking  a 


338        THE  SOURCES  AND  MODES  OF  INFECTION 

source  in  a  sparsely  inhabited  region.  Some  cities,  as  Liver- 
pool, Boston  and  New  York,  have  spent  large  sums  to  bring 
clean  water  from  long  distances.  Other  cities,  notably  Chi- 
cago, have  secured  good  water  by  the  construction  of  expen- 
sive works  to  remove  sewage  from  the  watershed.  Many 
cities,  when  there  is  only  a  limited  danger  of  pollution,  ac- 
complish much  by  a  continuous  patrol  of  the  watershed 
and  the  removal  of  minor  sources  of  pollution  under  general 
or  special  nuisance  laws.  In  many  states  this  duty  of  pro- 
tection has  been  laid  upon  the  state  boards  of  health,  and 
in  some  instances  cooperation  between  states  becomes 
necessary. 

Purification  of  Water.  —  Unfortunately  it  often  happens 
that  it  is  physically  impossible  for  a  municipality  to  obtain 
a  sufficient  supply  of  water  which  is  not  subject  to  dangerous 
pollution.  Purification  then  becomes  a  necessity,  and  owing 
to  the  labors  of  a  long  line  of  chemists,  engineers  and  bacteri- 
ologists, several  efficient  and  economical  methods  for  accom- 
plishing this  have  been  developed.  First  among  these  is 
filtration.  There  are  various  methods  of  filtration,  applica- 
ble to  different  waters  and  different  localities,  and  it  is  the 
business  of  specialists  to  devise  the  best  system  for  each  city 
confronted  by  the  problem.  Efficient  filtration  will  remove 
over  99  per  cent  of  the  contained  bacteria,  but  cannot  be  relied 
upon  to  remove  amebiK.  Hence  filtration  will  not  protect 
against  amebic  dysentery,  but  it  will  protect  against  the 
bacillary  form  and  against  tyjohoid  fever  and  cholera.  That 
it  is  efficient  against  typhoid  fever  is  shown  by  the  experience 
of  London,  Berlin,  Zurich,  Hamburg,  Lawrence,  Albany, 
Paterson,  Philadelphia  and  many  other  cities,  and  the  re- 
moval of  cholera  spirilla  was  beautifully  shown  by  the  ex- 
perience of  Altona  in  1893.  The  storage  of  water  rapidly 
removes  bacteria  by  sedimentation  and  through  the  death  of 
the  organisms,  and  is  often  a  us(^ful  adjunct  to  filtration, 
notably  so  in  the  case  of  some  of  the  London  water  companies. 
The  boiling  of  water  is  an  effectual  means  of  destroying  dan- 


INFECTION  BY  FOOD  AND  DRINK  339 

gerous  bacteria,  and  as  a  domestic  measure  it  is  sometimes 
extremely  useful. 

The  use  of  hypochlorite  of  lime  (commercial  bleaching 
powder)  has  within  a  short  time  come  into  use  for  the  pur- 
pose of  sterilizing  municipal  water  supplies.  While  this 
method  of  protection  had  been  used  in  England  as  a  tem- 
porary expedient,  its  first  use  as  a  permanent  method  of 
treatment  seems  to  have  been  by  Leal,  at  Boonton,  N.  J., 
in  1908.^  A  high  degree  of  safety  seems  to  be  secured  at  a 
low  cost.  The  subject  has  been  investigated  also  by  Clark 
and  Gage,^  Phelps,  Park,  Pratt  and  others.  The  process  has 
been  used  at  East  Providence,  R.  I.,  Poughkeepsie,  Chicago 
and  other  places.^ 

Infection  by  Ice. 

Danger  Exaggerated.  —  The  use  of  ice  from  polluted 
sources  has  always  been  viewed  with  some  alarm,  and  when 
it  became  known  from  the  work  of  Prudden^  and  others  that 
the  bacilli  of  typhoid  fever  live  for  some  months  when  frozen 
into  ice,  the  alarm  was  believed  to  be  well  founded.  But 
further  researches  (see  page  10)  have  shown  that  in  the 
freezing  of  ice  under  normal  conditions  a  large  proportion 
of  the  bacteria  in  the  ice  are  frozen  out,  and  those  that  remain 
tend  to  die  off  quite  rapidly,  somewhat  as  they  do  in  water. 
Hence  theoretically  little  danger  is  to  be  apprehended  from 
the  use  of  ice  cut  from  water  considerably  polluted,  even 
so  polluted  that  if  the  water  itself  were  used  it  would 
probably  cause  disease.  There  is  very  little  epidemiological 
evidehce  that  ice  has  been  the  cause  of  sickness.  The  litera- 
ture relating  to  the  subject  was  collected  by  Sedgwick  and 

1  Leal,    Fuller,    Johnson,  Papers  read  at  the  29th  Annual  Con- 
vention of  the  American  Water  Works  Association,  1909. 

2  J.  N.  Eng.  Water  Works  Ass.,  1909,  XXII,  302. 

^  Discussion  of  a  paper  by  Phelps  at  a  recent  meeting  of  the  Boston 
Society  of  Civil  Engineers,  Abst.  Eng.  Rec,  1910,  XLI,  80. 
*  Prudden,  Med.  Rec,  N.  Y.,  1887,  XXXI,  341. 


340       THE  SOURCES  AND  MODES  OF   INFECTION 

Winslow  ^  in  1902.  An  outbreak  the  exact  nature  of  which 
was  not  determined  occurred  at  Rye  Beach,  N.  H.,  in  1875, 
due  presumably  to  the  use  of  ice  from  a  pond  grossly  polluted 
with  decaying  vegetable  matter.  A  single  case  of  typhoid  fever 
in  Connecticut  appeared  to  be  due  to  the  use  of  specifically 
Infected  ice.  Alleged  outbreaks  of  typhoid  fever  and  dysen- 
tery in  the  United  States,  and  of  typhoid  fever  in  Evesham, 
England,  and  Rennes,  France,  were  also  noted  by  the  above- 
named  authors,  but  the  evidence  was  far  from  conclusive. 
More  recently  Hutchings  and  Wheeler  ^  report  an  outbreak 
of  typhoid  fever  in  a  hospital  at  Ogdensburg,  N.  Y.  Many 
were  attacked,  and  the  disease  was  suspected  to  be  due  to 
the  use  of  ice.  An  examination  of  the  ice  in  the  ice  house 
showed  that  some  of  it  contained  visible  dirt  from  which 
colon  and  typhoid  bacilli  were  isolated.  A  certain  lot  of 
ice  harvested  the  winter  before  began  to  be  used  on  Sep- 
tember 26.  Eight  cases  of  typhoid  fever  developed  from 
October  2  to  5  and  subsequent  cases  followed  until  some 
time  in  November,  involving  in  all  39  persons.  The  earliest 
cases  had  a  temperature  of  104°  and  105°  on  the  first  day. 
An  examination  of  the  ice  in  the  ice  house  showed  that  it 
contained  visible  dirt  from  which  colon  and  typhoid  bacilli 
were  isolated,  the  latter  determined  by  agglutination. 
Dr.  H.  W.  Hill  *  suggests  that  the  evidence  in  this  case  is  far 
from  conclusive,  because  6  days  is  a  very  short  period  of 
incubation,  and  for  8  cases  to  develop  in  9  days  would  be 
still  more  unusual,  and  to  have  the  cases,  after  so  short  an 
incubation,  develop  a  temperature  of  104°  and  105°  on  the 
first  day  is  even  more  remarkable.  Hill  thinks  that  this 
indicates  an  infection  before  the  use  of  the  ice,  and  he  calls 
attention  to  the  fact  that  typhoid  outbreaks  in  hospitals 

*  Sedgwick  and  Winslow,  Mem.  Am.  Acad.  Arts  &  Sc,    1902,  XII, 
No.  5,  472. 

2  Ilutoliinfrs  and  Wheeler,  Am.  J.  M.  Sc,  Phila.,  1903,  n.  s.,  CXXVI, 
G80. 

3  Hill,  .Address,  National  Ice  Association  of  Amcrcia,  N.  York,  1910. 


INFECTION  BY  FOOD  AND  DRINK  341 

for  the  insane  due  to  other  causes  are  by  no  means  rare. 
If  typhoid  bacilli  really  survived  in  the  ice  he  says  that  it 
would  indicate  a  persistence  of  a  month  over  what  has  ever 
been  observed  in  experiments.  At  Batangas  in  the  Philip- 
pines ^  an  outbreak  of  bacillary  dysentery  at  the  army  post 
was  said  to  be  due  to  contaminated  artificial  ice,  but  no 
data  were  given.  Park,  in  the  paper  cited  below,  refers  to 
a  small  outbreak  of  tj'phoid  fever  due  to  ice  cut  from  a  pond 
where  sewage  flowed  onto  ice  already  formed  and  then 
became  frozen.  Anderson  -  reports  an  outbreak  at  Lexing- 
ton, Va.,  possibly  due  to  artificial  ice  made  from  spring 
water  polluted  with  typhoid  excreta,  from  which  water  he 
isolated  typhoid  bacilli,  proved  to  be  such  by  cultural  and 
agglutination  tests.  Hamer^  refers  to  a  possible  instance 
of  ice-borne  typhoid  in  London  in  1898.  Judging  from  the 
small  number  and  indefinite  character  of  these  reports,  it 
appears  that  there  is  little  direct  evidence  of  danger  from  ice. 
In  the  outbreak  reported  by  Anderson  and  in  the  one  in  the 
Philippines  the  ice  was  artificial.  With  such  artificial  ice  the 
danger  must  be  very  much  greater  than  in  the  case  of  nat- 
ural ice,  for  in  the  former  the  bacilli  are  not  excluded  dur- 
ing the  process  of  freezing  and  little  time  is  allowed  for 
their  natural  death  in  the  ice.  The  one  noted  instance 
of  infection  by  natural  ice  which  has  seemed  most  con- 
clusive has  been  showTi  by  Hill  to  have  no  significance. 
There  is  on  the  other  hand  strong  epidemiological  evidence 
that  ice  is  not  a  factor  of  much  moment  in  the  causation 
of  disease.  Hundreds  of  thousands  of  tons  of  ice  are  cut 
from  sewage-polluted  waters  in  the  United  States,  but 
sickness  does  not  appear  to  follow  the  use  of  this  ice  in 
drinking  water.  Park  ^  has  studied  this  point  in  New  York 
City,  where  four-fifths  of  the  ice  is  cut  from  the  markedly 

1  Rep.  Bu.  Health,  P.  I.,  1908-9,  54. 

2  Anderson,  Med.  Rec,  N.  Y.,  1908,  LXXIV,  909. 

5  Hamer,  Rep.  Med.  Off.  Health,  Lond.,  1904,  Appendix  I. 
*  Park,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  731. 


342       THE  SOURCES  AXD   MODES   OF  INFECTION 

contaminated  Hudson  River.  Vast  quantities  of  this  ice  are 
used  in  drinking  water,  and  if  it  is  the  bearer  of  typhoid 
fever  there  should  begin  a  noticeable  increase  of  the  disease 
when  the  use  of  the  new  ice  commences  in  March,  and  this 
increase  should  continue  during  April  and  May.  During  the 
ten  years  studied  by  Park  no  such  increase  was  noted,  and 
no  outbreak  occurred  which  could  be  attributed  to  ice. 

Infection  hy  Milk. 

Character  of  Outbreaks.  —  It  has  long  been  known  that 
some  of  the  common  contagious  diseases  of  human  beings 
may  be  transmitted  by  means  of  milk.  The  only  diseases 
that  are  definitely  known  to  be  so  carried  are  typhoid  fever, 
scarlet  fever  and  diphtheria.  There  is  no  reason  why  dysen- 
tery and  cholera,  and  perhaps  otlier  diseases,  should  not  be 
transmitted  in  the  same  way,  but  no  evidence  of  it  has  come 
to  my  knowledge,  except  that  referred  to  by  Kober,^  who 
states  that  McNamara  in  Calcutta,  in  1872,  traced  an  out- 
break of  cholera  to  an  infected  dairy.  Outbreaks  of  the 
above  diseases  have  been  reported  from  time  to  time,  and 
have  been  studied  by  Hart,  Kober  and  others,  but  the  latest 
tabulation  and  the  fullest  consideration  of  the  subject  are 
to  be  found  in  Bulletin  56,  Hygienic  Laboratory,  United 
States  Public  Health  and  Marine  Hospital  Service,  1909. 
Milk  outbreaks  of  these  diseases  have  an  explosive  character, 
such  as  is  shown  by  water-borne  outbreaks  of  typhoid  fever. 
In  scarlet  fever  and  diphtheria  the  explosive  character  is  owing 
to  the  shorter  incubation  of  these  diseases,  more  pronounced 
than  it  is  in  typhoid  fever.  A  milk  outbreak  is  determined 
to  be  such  from  the  presence  of  an  excessive  number  of  cases 
on  a  particular  milk  supply  which  cannot  be  accounted  for 
in  any  otlier  way.  From  three  to  five  cases  within  a  few 
days  on  a  route  covered  by  one  wagon  in  a  city  with  an 
average  typhoid  death  rate  is  highly  suspicious,  and  in  most 

'    IvoIkt,  J.  Am.  M.  Ass.,  Chicago,  1!)()7,  XLIX,  1001. 


INFECTION  BY  FOOD   AND  DRINK  343 

instances  proves  to  be  the  beginning  of  an  outbreak.  The 
more  the  customers  of  a  dealer  are  scattered,  the  stronger 
is  the  evidence.  Care  must  be  taken  to  exclude  all  other 
sources,  such  as  neighborhood  or  family  contact,  water,  ice, 
shellfish  or  other  foods.  Milk  outbreaks  often  prevail  more 
extensively  among  the  well-to-do,  owing  to  their  greater  con- 
sumption of  milk,  and  a  typhoid  milk  outbreak  usually  shows 
a  high  percentage  of  children  attacked.  Often  the  source  of 
infection  can  be  found.  In  only  two  instances  reported  by 
Konradi  ^  and  Shoemaker  ^  has  the  typhoid  bacillus  been 
isolated  from  milk,  and  in  only  four  instances  has  the 
diphtheria  bacillus  been  recovered.^ 

Number  of  Outbreaks.  —  The  number  of  outbreaks  pretty 
definitely  traced  to  milk  is  quite  large.  Trask,  in  the  Hygi- 
enic Laboratory  Bulletin  referred  to,  tabulated  179  outbreaks 
of  typhoid  fever,  51  of  scarlet  fever,  23  of  diphtheria  and 
7  of  sore  throat.  Besides  these  Hart  reported  51  of  typhoid 
fever,  and  Busey  and  Kober  86  of  typhoid  fever,  59  of  scarlet 
fever,  21  of  diphtheria,  making  in  all  316  outbreaks  of  typhoid 
fever,  125  of  scarlet  fever,  51  of  diphtheria  and  7  of  sore 
throat.  In  these  are  not  included  the  90  outbreaks  tabu- 
lated by  Caroe.  This  is  certainly  an  impressive  aggregate, 
but  it  must  be  remembered  that  these  records  cover  a  period 
of  perhaps  half  a  century.  To  determine  within  any  degree 
of  accuracy  how  large  a  part  milk  plays  in  the  spread  of 
these  diseases  is  difficult,  but  it  seems  to  me  that  the  tend- 
ency at  the  present  time  is  to  exaggerate  its  importance. 
Schiider  *  found  that  of  640  outbreaks  of  typhoid  fever  462 
were  caused  by  water  and  110  by -milk,  but  it  is  highly  im- 
probable that  cases  caused  respectively  by  water  and  by  milk 

1  Konradi,  Centralbl.  f.  Bakteriol.  [etc.],  Jena,  I  Abt.  Orig.,  XL,  31. 

2  Shoemaker,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  1748. 

'  Nuttall  and  Graham-Smith,  The  Bacteriology  of  Diphtheria, 
Cambridge,  1908,  326. 

*  Schiider,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1901, 
XXXVIII,  343. 


344       THE  SOURCES  AND  MODES  OF  INFECTION 

occur  in  any  such  ratio  in  the  United  States.  Most  of  the 
water-borne  typhoid  fever  does  not  occur  in  outbreaks,  but 
is  due  to  the  continuous  pollution  of  municipal  supplies. 
Milk-borne  typhoid  fever,  on  the  other  hand,  probably  does 
occur  chiefly  in  the  form  of  outbreaks.  During  the  last  four 
years,  in  Providence,  155  of  the  600  milk  dealers  have  had 
one  or  more  cases  of  typhoid  fever  on  their  routes.  In  only 
9  instances  have  there  been  more  than  2  cases  on  a  single 
route  within  a  week.  Investigation  promptly  showed  that 
in  3  instances  the  groups  of  cases  were  due  to  personal  con- 
tact, and  in  the  other  6  instances  an  unmistakable  milk 
outbreak  developed.  It  is  true  that  some  epidemiologists 
assume  that  a  considerable  number  of  sporadic  cases  are  due 
to  milk,  but  the  evidence  appears  to  be  the  other  way.  I 
think  that  a  study  of  the  distribution  of  typhoid  cases  on 
milk  routes  in  Washington,  as  shown  in  diagrams  in  bulletins 
35,  44  and  52  of  the  Hygienic  Laboratory,  United  States 
Public  Health  and  Marine  Hospital  Service,  bears  out  my 
contention  that  outbreaks  of  typhoid  fever  due  to  milk  are 
not  likely  to  escape  notice  if  the  cases  are  daily  tabulated 
according  to  milk  supply.  Furthermore,  these  charts  show 
that  there  is  little  excess  of  typhoid  fever  on  individual  milk 
supplies  except  in  those  instances  where  there  is  a  noticeable 
outbreak. 

Fewer  Outbreaks  in  Large  Cities.  —  It  is  also  to  be  noted 
that  v(Ty  few  outbreaks  aro  r(>ported  from  the  large  cities 
like  New  York,  Chicago  and  Philadelphia,  due  perhaps  to 
the  fact  that  the  chemical  and  bacteriological  changes  in  the 
milk  resulting  from  the  long  haul  necessary  for  such  cities 
are  unfavorable  for  the  typhoid  bacillus.  In  the  country, 
milk  outbreaks  are  not  likely  to  be  a  factor  of  moment,  as 
large  milk  routes  are  not  common.  It  is  in  the  medium-sized 
and  smaller  cities  and  villages  that  most  of  the  milk  out- 
breaks are  reported.  It  will  be  noted  that  though  scores  of 
outbreaks  of  typhoid  fev(T  may  occur  each  j'ear,  they  do  not 
include  more  than  a  small  fraction  of  the  total  typhoid  fever. 


INFECTION  BY  FOOD  AND  DRINK  345 

It  may  be  claimed  that  only  a  small  proportion  of  the  milk- 
borne  outbreaks  are  recognized  as  such,  but  I  cannot  think 
that  this  is  so  in  the  English  cities  and  the  better  class  of 
American  cities.  In  Providence  during  the  last  twenty-five 
years  there  have  been  nine  outbreaks  of  typhoid  fever,  includ- 
ing 363  cases,  or  about  8  per  cent  of  the  total  occurring  during 
that  time.  But  the  typhoid  death  rate  in  Providence  is 
below  the  average,  so  that  8  per  cent  in  Providence  would 
probably  be  equivalent  to  not  over  4  per  cent  in  the  average 
American  city  with  its  polluted  water  supply  and  numerous 
privy  vaults.  In  only  a  few  cities  have  Trask,  Hart,  and  Busey 
and  Koberbeen  able  to  find  records  of  more  than  two,  or  more 
rarely  three,  outbreaks ;  yet  we  can  scarcely  believe  that  milk 
outbreaks  could  have,  except  rarely,  escaped  detection  in  the 
English  cities,  or  in  such  cities  as  Boston,  Worcester,  Spring- 
field, Rochester,  Baltimore,  Philadelphia  and  New  York. 

Amount  of  Typhoid  Fever  Due  to  Milk.  —  The  city  of 
Washington  is  reported  as  showing  an  excessive  amount  of 
milk-borne  typhoid  fever.^  In  1906,  79,  or  9  per  cent,  of  the 
866  cases  investigated  by  the  commission,  were  traced  to  milk; 
in  1907,  31,  or  5  per  cent,  of  635  cases  investigated;  and  in 
1908,  54,  or  8  per  cent,  of  679  cases.  According  to  figures 
furnished  by  Dr.  Woodward,  Health  Officer  of  Washington, 
the  number  of  typhoid  cases  due  to  milk  during  the  three 
years  was  139,  which  gives  a  percentage  of  4.6.  The  com- 
mission considers  that  10  per  cent  of  the  typhoid  fever  in 
Washington  is  due  to  milk.  These  percentages,  however,  seem 
to  me  unfair,  as  doubtless  all  the  outbreaks  were  reported, 
and  the  percentages  should,  from  the  standpoint  of  the  present 
consideration,  be  based  on  the  total  number  of  cases  reported 
in  the  city,  and  not  on  the  cases  studied  and  of  known  origin. 
This  gives  a  percentage,  as  above  stated,  of  4.6  of  the  typhoid 
fever  in  Washington  during  the  three  years  1906-08  as  due 
to  milk-borne  typhoid.     The  importance  and  value  of  the 

1  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Hyg.  Lab.,  Bull.  No.  35, 
59;  No.  44,  46;  No.  52,  100. 


346       THE  SOURCES  AND  MODES  OF  INFECTION 

reports  on  typhoid  fever  in  Washington  have,  as  it  appears, 
given  a  rather  exaggerated  importance  to  the  danger  from 
milk.  That  there  was  a  certain  amount  of  typhoid  fever  in 
Washington  due  to  milk,  during  the  three  years  in  question,  is 
no  reason  for  assuming  a  similar  percentage  of  milk-borne 
typhoid  fever  for  the  other  cities  of  the  country.  Trask  was 
able  to  find  during  the  years  1903-07  about  1900  cases  in 
the  United  States  traced  to  milk.  During  this  period  there 
were  in  the  registration  area  57,023  deaths,  and  the  total  num- 
ber in  the  whole  country  must  have  been  at  least  double,  or 
114,000.  The  fatality  is  probably  not  over  10  per  cent,  so 
that  there  must  have  been  at  least  1,000,000  cases.  Nine- 
teen hundred  is  0.19  per  cent,  which  is  very  different  from  the 
10  per  cent  now  commonly  assumed  as  due  to  milk.  I  do  not 
of  course  believe  that  all  the  milk  outbreaks  were  reported, 
but  the  number  would  have  to  be  increased  fifty-fold  to 
equal  10  per  cent,  and  it  can  scarcely  be  believed  that  98  per 
cent  of  all  milk  outbreaks  fail  of  recognition. 

Scarlet  Fever  and  Diphtheria.  —  Scarlet  fever  and  diph- 
theria are  certainly  much  more  rarely  transmitted  by  means 
of  milk  than  is  typhoid  fever.  Although  the  percentage  of 
typhoid  fever,  scarlet  fever  and  diphtheria  due  to  milk  is 
small,  the  danger  is  a  real  one  and  the  aggregate  of  cases  not 
inconsiderable,  and  their  occurrence  should,  if  possible,  be 
guarded  against. 

Animal  Sources.  —  The  infection  of  milk  with  the  above 
diseases  is  almost  invariably  from  human  sources.  There  is 
no  evidence  to  show  that  cows  may  be  infected  with  the 
bacillus  of  typhoid  fever,  and  the  contamination  of  the  milk 
by  drinking  sewage-polluted  water  does  not  occur.  Scarlet 
fever  also  does  not  appear  to  be  an  animal  disease.  Power 
and  Klein  in  England  believed  that  they  had  found  the  cause 
of  milk-borne  outbreaks  of  scarlet  fever  in  the  sickness  of  the 
cows  supplying  the  milk.  These  findings  have  not  been  sub- 
stantiated, and  the' micrococcus  which  Klein  believed  was 
the  cause  of  the  disease  has  not  been  accepted  as  such  by 


INFECTION  BY  FOOD  AND  DRINK  347 

bacteriologists.  While  many  of  the  lower  animals  may  be 
successfully  inoculated  with  diphtheria,  the  disease  does  not 
appear  often  to  occur  spontaneously  among  them.  Never- 
theless two  milk-borne  outbreaks  have  been  traced  to  diph- 
theria of  the  cows'  udder.  One  of  these  was  reported  by  Dean 
and  Todd^  and  the  other  by  Ashby.^ 

Human  Sources.  —  Besides  the  bacteriological  evidence 
that  milk  rarely  acquires  its  infection  of  these  diseases  from 
animals,  we  have  the  direct  evidence  that  in  a  considerable 
number  of  outbreaks  the  milk  is  known  to  have  been  handled 
by  persons  -sick  with  the  disease  or  carrying  its  organisms. 
Trask  ^  says  that  in  113  of  the  179  outbreaks  of  typhoid  fever 
reported  by  him  an  infected  person  was  found  to  have 
handled  the  milk,  and  in  only  4  instances  was  the  infection 
reported  to  have  come  from  polluted  water  used  in  washing 
utensils,  and  in4others  to  the  use  of  milk  bottles  from  infected 
houses.  In  35  of  the  57  scarlet-fever  outbreaks  an  infected 
person  was  found  to  have  handled  the  milk,  and  3  others  were 
due  to  the  use  of  bottles  from  infected  houses.  Of  the  23 
diphtheria  outbreaks,  18  were  traced  to  handlers  of  the 
milk.  A  study  of  the  details  of  milk  outbreaks  shows  that  in  a 
large  proportion  the  infecting  case  was  not  recognized  as  such, 
that  the  symptoms  were  mild  or  atypical,  that  infection  oc- 
curred during  the  incipient  stage,  or  that  the  person  was 
merelj^  a  carrier.  Infection  may  occur  at  any  time  during  the 
handling  of  milk,  from  the  beginning  of  milking  until  the  milk 
is  delivered  to  the  consumer,  and  it  may  also  be  caused  by  those 
who  take  care  of  the  pails,  cans,  bottles,  strainers,  drums,  etc. 
Outbreaks  are  believed  to  have  been  caused  by  the  tasting  of 
milk  by  infected  dealers,  and  in  the  instance  reported  by 
Shoemaker  ^  a  convalescent  patient  was  in  the  habit  of  start- 

1  Dean  and  Todd,  J.  Hyg.,  Cambridge,  1902,  II,  194. 

2  Ashby,  Pub.  Health,  Lond.,  1906-07,  XIX,  145. 

»  Trask,  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Hyg.  Lab.,  Bull. 
No.  41,  25  et  .seq. 

^  Shoemaker,  J.  Am.  M.  Ass.,  Chicago,  1907,  LXVIII,  1748. 


348       THE  SOURCES  AND  MODES  OF  INFECTION 

ing  a  siphon  from  the  milk  drum  by  sucking  the  tube.  It 
is  also  believed  by  many  that  flies  are  an  important  factor 
in  the  contamination  of  milk. 

Protection  of  Milk.  —  There  are  various  ways  in  which  the 
danger  from  infected  milk  may  be  avoided. 

First.  If  all  recognized  cases  of  the  diseases  just  considered 
are  promptly  reported,  and  proper  measures  of  isolation  are 
insisted  on,  there  will  be  a  considerable  decrease  in  the 
amount  of  milk-borne  infection.  When  such  a  disease  occurs 
in  the  family  of  a  milk  producer  or  dealer  the  patient  should 
usually  be  removed  from  the  premises,  and  the  vessels,  etc., 
if  possibly  infected,  should  be  disinfected.  The  greatest  diffi- 
culty is  encountered  in  the  management  of  convalescents, 
and  particularly  carriers,  and  it  is  the  view  of  most  health 
officers  that  the  latter  should  be  permanently  excluded  from 
the  milk  business.  Unfortunately  there  are  many  mild  cases 
of  contagious  disease  which  are  never  recognized  and  are  not 
likely  to  be.  Moreover,  persons  in  the  incipient  stage  are 
quite  likely  to  transmit  the  disease,  and  we  cannot  hope  for 
much  earlier  recognition  than  we  now  have.  Hence  for  the 
prevention  of  outbreaks  from  these  unknown  sources  we  must 
rely  on  other  methods. 

Second.  It  is  possible  to  reduce  the  chances  of  infection 
by  insisting  on  cleaner  methods  in  handling  milk  and  requir- 
ing the  sterilization  of  all  vessels,  particularly  of  bottles.  If 
all  handlers  would  wash  their  hands,  and  keep  their  hands 
out  of  the  milk  and  out  of  tlu-  vessels,  there  would  be  no  milk 
outbreaks.  But  we  can  hope  for  no  very  radical  improvement 
as  regards  the  cleanliness  of  milkers,  farm  hands  and  peddlers. 

Third.  The  pasteurization  of  the  milk  by  the  dealer  before 
delivery  would  also  decrease  to  a  large  extent  the  amount  of 
milk-borne  disease,  for  a  study  of  outbreaks  shows  that  in  a 
large  proportion  the  infection  of  the  milk  takes  place  on  the 
farm.  But  there  is  also  consid(M'al)le  risk  of  contamination  in 
the  hands  of  the  deader  after  pasteurization.  For  this 
reason  much  attention  h;is  been  devoted  to  the  problem  of 


INFECTION  BY  FOOD  AND  DRINK  349 

pasteurization  in  bottles  so  that  the  milk  may  with  cer- 
tainty be  delivered  to  the  consumer  free  from  infection. 
Pasteurization  of  beer  in  bottles  has  long  been  practiced  by 
-brewers,  and  investigators^  and  milk  dealers  have  adapted 
the  methods  of  brewers  to  the  treatment  of  milk  and  some 
large  milk  dealers  are  now  delivering  milk  prepared  in  this 
way. 

Fourth.  In  the  absence  of  pasteurization  by  the  dealer, 
doubtless  the  most  successful  way  of  preventing  milk-borne 
disease  at  the  present  time  is  for  the  public  to  consume  no 
milk  except  that  which  has  been  pasteurized  or  scalded  in 
the  house.  Many  object  to  the  trouble  and  do  not  like  the 
taste  of  heated  milk,  so  that  this  practice  is  not  likely  to 
become  universal.  Moreover  outbreaks  have  occurred,  as 
at  Bristol,^  where  milk  pasteurized  in  an  institution  had 
been  afterwards  infected  by  a  maid. 

It  therefore  seems  that  while  it  is  possible  materially  to 
lessen  by  the  above  methods  the  amount  of  milk-borne 
disease,  we  cannot  hope  at  present  entirely  to  do  away  with 
the  danger  of  milk-borne  outbreaks  of  the  diseases  we  have 
been  considering. 

Ice  Cream.  —  As  milk  is  so  frequently  the  bearer  of  dis- 
ease, it  is  not  surprising  that  outbreaks  have  at  times  been 
attributed  to  food  products  derived  from  milk.  Thus 
Soper^  reported  an  outbreak  due  to  the  use  of  cream  on 
breakfast  food,  and  one  of  the  outbreaks  reported  by  Trask 
was  due  to  whipped  cream.  Sedgwick  and  Winslow^  col- 
lected records  of  four  outbreaks  of  typhoid  fever  due  to  the 
use  of  ice  cream,  and  another  has  been  reported  by  Barras.^ 

1  North,  Med.  Rec,  N.  York,  1911,  LXXX,  111. 

2  Davies  and  Walker,  Proc.  Roy.  Soc.  Med.,  Lend.,  1808,  Epi- 
demiol. Sec,  175. 

3  Soper,  J.  Mass.  Ass.  Bds.  Health,  Bost.,  1904,  XIV,  68. 

*  Sedgwick  and  Winslow,  INIem.  Am.  Acad.  Arts  &  Sc,  1902,  XII, 
No.  5,  475. 

*  Barras,  Lancet,  Lond.,  1904,  II,  1281. 


350       THE  SOURCES  AND  MODES  OF  INFECTION 

A  quite  remarkable  ice-cream  outbreak  of  typhoid  fever 
occurred  in  Eccles  and  Manchester  in  November,  1910, 
involving  108  cases.^  The  makers  and  sellers  of  the  ice 
cream  were  two  Italians  in  a  tenement  house  in  Manchester. 
Professor  Delepine,  who  investigated  the  outbreak  bacterio- 
logically,  was  of  the  opinion  that  the  ice  cream  must  have 
been  so  grossly  infected  as  only  to  be  explained  by  a  multi- 
plication of  the  bacilli  in  the  materials  used  after  they  had 
been  heated  and  before  freezing.  Of  the  13  persons  living 
in  the  house  with  the  Italians  there  were  6  whose  blood  gave 
a  positive  Widal  reaction.  No  examination  of  their  excreta 
appears  to  have  been  made. 

Buchan^  refers  to  an  outbreak  of  scarlet  fever  due  to  ice 
pudding  and  reported  by  Buchanan  in  1875.  He  also  notes 
two  outbreaks  due  to  the  infection  of  ice  cream  with 
B.  enteritidis  (Gaertner).  Buchan  made  many  examina- 
tions of  market  ice  cream  in  Birmingham  and  suggested  a 
bacteriological  standard  for  ice  cream  and  a  set  of  excellent 
rules  for  its  manufacture. 

Another  typhoid  outbreak  due  to  ice  cream  has  recently 
been  reported  from  Fort  Sill,  Okla.,  where  20  cases  were 
due  to  eating  ice  cream  from  the  neighboring  town  of 
Lawton.^ 

Butter.  —  While  it  has  been  shown  that  pathogenic  bacilli 
may  live  for  some  time  in  butter,  only  one  outbreak  seems 
to  have  been  reported  as  arising  from  the  use  of  this  sub- 
stance. This  is  probably  due  partly  to  the  fact  that  the 
germs  must  die  off  pretty  rapidly,  leaving  perhaps  only  a 
few  survivors,  and  partly  to  the  difficulty  of  tracing  an 
outbreak  to  such  a  source. 

An  outbreak  of  diphtheria  at  Lewiston,  Minn.,  was  be- 
lieved to  have  been  caused  by  eating  infected  butter. 
There  had  been  no  diphtheria  in  the  place  until  a  boy  re- 

1  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1910-11,  XL,  18. 

2  Buchan,  J.  Ilyg.,  CambridRe,  1910,  X,  93. 

'  Rep.  Surg.  Gen.  Army,  Wasli.,  1909-10,  45. 


INFECTION  BY  FOOD  AND  DRINK  351 

turned  from  the  "  Twin  Cities  "  after  an  attack  of  diph- 
theria. The  milk  from  the  farm  where  he  Uved  was  sent  to 
a  creamery  and  every  family  in  the  place,  in  which  there 
was  diphtheria,  was  found  to  have  used  butter  from  this 
creamery.  Experiments  showed  that  diphtheria  bacilli  can 
live  in  butter  for  a  month. ^ 

Epidemic  Sore  Throat  or  Tonsillitis.  —  According  to 
Winslow^  outbreaks  of  what  is  often  called  septic  sore  throat 
have  many  times  been  reported  in  England  and  have  been 
showTi  to  be  associated  with  particular  milk  supplies. 
Some  of  these  outbreaks  more  or  less  resemble  scarlet  fever 
or  include  some  cases  of  typical  scarlet  fever.  In  others 
there  is  no  reason  to  consider  the  infection  of  a  scarlet-fever 
nature.  Winslow,  without  a  systematic  search  of  the 
literature,  was  able  to  find  12  outbreaks  of  this  character. 
In  4  of  these  outbreaks  there  was  no  evidence  whatever  as 
to  the  original  source  of  the  disease.  In  4  others  there  was 
a  dubious  connection  with  some  disease  in  cows.  At  Glas- 
gow and  Colchester,  Winslow  thinks  that  there  was  fairly 
strong  evidence  connecting  the  outbreaks  with  an  in- 
flammatory condition  of  the  cow's  udder.  At  Rothesay 
probability  pointed  to  human  infection  and  at  Working 
there  had  been  both  human  quinsy  and  bovine  udder  in- 
flammation on  the  farm.  Another  outbreak^  occurred  in 
Christiania  in  1908  and  it  was  not  determined  whether  it 
had  a  bovine  or  human  origin. 

Sore  Throat  in  Boston.  —  The  first  recorded  American 
outbreak  occurred  in  Boston  in  1911  and  was  reported  by 
Winslow  as  above.  In  Boston  and  the  adjoining  towns  of 
Brookline  and  Cambridge  there  were,  during  a  short  period 
in  May,  probably  not  far  from  2000  cases,  of  which  48 
proved  fatal  and  many  more  were  quite  severe.     Many  of 

1  Rep.  State  Bd.  Health,  Minn.,  1911,  203. 

2  Winslow,  J.  Infect.  Dis.,  Chicago,  1912,  X,  73. 

3  Norsk  Mag.  f.  Lagevidenskahen,  1908,  LXIX,  585,  811:  Ref. 
J.  M.  Ass.,  Chicago,  1912,  LVIII. 


352       THE  SOURCES  AND  MODES  OF  INFECTION 

the  cases  developed  abscesses,  and  not  a  few  general  septic 
infection,  as  has  been  the  case  in  European  outbreaks. 
The  outbreak  was  quite  clearly  traced  to  milk  and  cream 
supplied  by  the  Deerfoot  Farm  Dairy  in  Southboro.  This 
dairy  and  the  farms  supplying  it  were  under  the  constant 
supervision  of  a  trained  bacteriologist  and  the  cows  were 
frequently  inspected  by  a  veterinary  physician;  the  milk 
received  as  little  handling  as  possible  and  indeed  everything 
was  done  to  deliver  milk  of  a  high  bacterial  standard  and 
free  from  infection.  It  seemed  improbable  that  there  wan 
any  udder  disease  among  the  cows  which  could  have  given 
rise  to  the  trouble.  The  farms  supplying  the  milk  are 
largely  located  some  distance  from  Boston  in  Southboro 
and  to  some  extent  in  the  adjoining  towns  of  Wcstboro, 
Framingham  and  Marlboro.  As  shown  by  the  investiga- 
tions of  Winslow  there  was  a  marked  prevalence  of  the  same 
disease  in  the  towns  of  Marlboro,  Southboro  and  Hudson 
all  through  April  and  May.  In  these  towns  the  disease 
appeared  to  pass  by  contact  from  person  to  person  in  prose- 
demic  fashion,  just  as  diphtheria  ordinarily  does,  except 
that  there  was  marked  and  sudden  excess  in  Marlboro  and 
Southboro  in  May,  coincident  with  the  Boston  outbreak. 
In  both  these  towns  much  Deerfoot  milk  is  sold,  but  none 
in  Hudson,  where  there  was  no  May  exacerbation.  Wins- 
low  is  of  the  opinion  that  the  milk  in  some  way  became 
infected  from  cases  or  carriers,  though  no  such  infection 
coukl  ])e  demonstrated.  As  streptococci  were  isolated  from 
the  internal  organs  of  fatal  cases  these  were  thought  to 
be  the  inf(X'ting  organisms.  Other  outbreaks  have  been 
reported  from  Baltimore  '  and  Cliicago.' 

Views  concerning  Tuberculosis.  —  Of  all  the  animal 
diseases  wliicli  are  transmissible  to  man  tu])erculosis  has 
received  the  most  attention.     After  many  years  of  discussion 

'   .1.  y\m.  M.  Ash.,  ChioaKo,  H)12,  LVllI,  110!). 

2   Miller  iiiul  (liippH,  J.  Am.  M.  Ahs.,  Chicago,  1912,  LVIII,  1111. 


INFECTION  BY  FOOD  AND  DRINK  353 

and  investigation  there  is  now  general  agreement  that  while 
the  two  types  of  tubercle  bacilli,  human  and  bovine,  are  dis- 
tinct and  quite  permanent,  they  are  reciprocally  infective, 
-though  not  to  the  same  degree.  That  human  beings  may 
become  infected  with  tuberculosis  derived  from  cattle  is  now 
generally  admitted,  but  there  is  as  yet  no  general  agreement 
as  to  the  amount  of  such  infection,  though  present  views  are 
not  so  divergent  as  those  of  a  few  years  ago.  The  question 
of  the  mode  of  infection  in  tuberculosis  and  the  source  of  the 
bacilli  is  so  largely  dependent  on  pathological  evidence  that 
it  is  very  difficult  for  one  who  is  not  a  pathologist  properly  to 
weigh  the  evidence.  Yet  in  view  of  the  lack  of  agreement 
among  pathologists  it  becomes  necessary  for  the  health  officer, 
who  must  take  definite  action  to  combat  the  disease,  to 
attempt  to  arrive  at  some  sort  of  conclusion.  It  seems  fair, 
from  the  evidence  thus  far  available,  to  draw  the  following 
conclusions: 

Bovine  Bacillus  may  infect  Man.  —  First.  The  bovine 
type  of  bacillus  is  capable  of  causing  infection  in  human 
beings.  This  is  shown  by  the  successful  inoculation  of  human 
beings  with  bovine  virus.  A  considerable  number  of  cases 
of  the  accidental  inoculation  of  veterinarians  and  laboratory 
workers  while  manipulating  animals  dead  with  tuberculosis 
have  been  reported  by  Pfeiffer,  Tscherning,  Naughton,  Cop- 
pez,  Priester,  Hartzell,  Grothan,  Jadasohn,  Ravenel,  de 
Jong,^  Salmon  ^  and  others.  In  most  cases  the  lesion  was 
local,  and  some  have  arguedr  that  this  is  strong  evidence  of 
weakened  ^virulence  for  man.  The  finding  of  the  bovine  type 
of  the  bacillus  in  human  beings  is  generally  considered  as 
furnishing  a  more  certain  demonstration  of  the  latter's  suscep- 
tibility to  the  disease.  As  will  be  again  referred  to,  the  Ger- 
man and  British  commissions,  and  various  Americans,  have 

1  Moss,  Johns  Hopkins  Hosp.Bull.,  1909,  XX, 39;  Cornet,  Nothnagel's 
Encyclopedia  of  Practical  Medicine,  Phila.  &  Lond.,  1907,  Tubercu- 
losis, 77. 

2  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Bull.  No.  33,  16. 


354       THE  SOURCES  AND  MODES  OF  INFECTION 

found  the  bovine  bacillus  in  from  16  to  25  per  cent  of  the 
cases  studied.  These  facts,  while  demonstrating  the  suscep- 
tibility of  human  beings  to  the  bovine  form  of  the  disease, 
do  not  indicate  definitely  to  what  extent  the  bovine  type 
prevails  in  man,  as  the  cases  examined  were  usually  specially 
selected. 

Feeding  Experiments.  —  Second.  Tuberculosis  may  be 
produced  experimentally  in  animals  by  the  ingestion  of  mate- 
rial containing  tubercle  bacilli.  Milk  known  to  be  infected 
with  tubercle  bacilli  has  been  in  numerous  instances  fed  to 
guinea  pigs,  rabbits,  dogs,  calves,  swine  and  monkeys,  and 
has  caused  fatal  tuberculosis  in  them.  This  has  been  demon- 
strated by  a  large  number  of  workers  in  all  parts  of  the  world. 
A  good  summary  of  previous  experiments  is  given  by  Mohler,' 
who  himself  produced  tuberculosis  by  feeding  guinea  pigs 
with  milk  from  tuberculous  cows.  Subsequent  experiments 
by  the  Bureau  of  Animal  Intlustry  -  show  that  while  guinea 
pigs  are  with  difficulty  infected  by  feeding,  hogs  are  very 
easily  infected,  the  primary  infection  apparently  occurring  in 
the  submaxillary  glands,  the  lungs  usually  becoming  second- 
arily infected.^  That  the  ingestion  of  tuberculous  material, 
especially  milk  from  creameries,  is  the  chief  cause  of  tuber- 
culosis in  swine,  is  the  opinion  of  the  officers  of  this  depart- 
ment and  of  Ravenel  and  Russell.^  The  more  recent  work 
of  Calmette  and  the  French  school,  while  not  always  including 
direct  experiments  with  milk,  show  that  material  containing 
tubercle  bacilli,  introduced  in  any  way  into  the  stomach  or 
intestines,  results  in  the  produc^tion  of  tul)erculosis,*and  even 
the  pupils  of  Fliigge  admit  that  the  ingestion  of  a  sufficient 
number  of  bacilli  will  cause  the  disease,  though  it  is  produced, 
they  say,  much  more  easily  by  inoculation  or  inhalation.     It 

»  Molilor,  U.  S.  Dopt.  Agric,  Bii.  An.  Ind.,  liull.  No.  44,  13. 
»  U.  S.  Dept.  Agric,  Bu.  An.  Iiid.,  Ciic.  83,  Bull.  Nos.  86,  88,  93. 
»  Bull.  No.  88,  40. 

*  Ravonol  and  Russell,  Am.  Piih.  llcalUi  Ass.  Rup.,  190G,  XXXII, 
Pt.  I,  13!». 


INFECTION  BY  FOOD  AND   DRINK  355 

is  also  generally  admitted  that  bacilli  may  be  absorbed 
through  the  intestines  without  leaving  any  lesion.  While 
some  pathologists  think  that  it  is  usually  possible  to  deter- 
,mine  the  route  of  infection  by  the  age  and  character  of  the 
lesions,  other  equally  good  men  do  not  consider  that  any  very 
reliable  conclusions  can  be  arrived  at  in  this  manner.  Under 
these  circumstances  it  appears  that  we  cannot  as  yet  appeal 
to  the  pathologists  for  a  definite  decision  as  to  the  mode  of 
infection  in  this  disease,  and  we  may  be  permitted  to  assume 
that  a  large  amount  of  tuberculosis  may  be  due  to  infection 
through  one  part  or  another  of  the  alimentary  canal. ^ 

Tubercle  Bacilli  in  Milk.  —  Third.  Tubercle  bacilli  are 
frequently  found  in  cows'  milk.  It  was  formerly  believed 
that  tubercle  bacilli  do  not  occur  in  cows'  milk  unless  the 
udder  is  diseased.  Nevertheless  various  observers  from  time 
to  time  have  reported  finding  the  bacilli  although  no  udder 
disease  was  evident.  Finally  Schroeder  and  Cotton"  showed 
that  frequently  the  feces  of  cattle  contain  large  numbers  of 
tubercle  bacilli,  although  the  animals  present  no  visible  symp- 
toms of  disease.  They  furthermore  showed  that  the  pollu- 
tion of  milk  with  infected  feces  is  the  most  common  source 
of  tubercle  bacilli  found  in  milk.  As  from  3  to  50  per  cent 
of  the  cattle  in  different  parts  of  the  United  States  react  to 
tuberculin,  and  probably  25  per  cent  of  the  cattle  in  Great 
Britain  are  infected,  it  is  not  surprising  that  market  milk  in 
these  countries  is  frequently  found  to  contain  tubercle  bacilli 
in  sufficient  numbers  to  cause  the  death  of  test  animals. 
Anderson  ^  gives  a  resume  of  the  literature  of  the  subject. 
Among  the  percentages  of  infected  milk  referred  to  are,  in 
Copenhagen,  14.3  per  cent ;  Boston,  21  per  cent  and  40  per  cent ; 
Liverpool,  5.2  per  cent  from  city  dairies,  13.4  per  cent  from 

^  For  other  references  to  the  causation  of  tuberculosis  through  the 
alimentar}'^  canal  see  p.  255. 

'  Schroeder  and  Cotton,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Bull.  No.  99. 

'  Anderson,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Hyg.  Lab.» 
Bull.  No.  41,  163. 


356       THE  SOURCES  AND  MODES  OF   INFECTION 

country  dairies,  though  later/  owing  to  the  efforts  of  the 
authorities  in  eradicating  the  disease,  the  percentage  in  city 
dairies  was  1.4  per  cent  and  in  country  dairies  was  7  per  cent; 
Genoa,  9  per  cent;  London,  22  per  cent;  and  Berlin,  28  per 
cent.  Recently  of  620  samples  of  milk  consigned  to  London, 
61,  or  11.6  per  cent,  were  found  to  contain  tubercle  bacilli.^ 
Anderson  found  6.72  per  cent  of  223  samples  of  market  milk 
in  Washington  to  contain  virulent  tubercle  bacilli.  Hess  ^ 
found  virulent  tubercle  bacilli  in  16  per  cent  of  107  samples 
of  New  York  market  milk  (not  bottled).  He  thinks  the 
reason  that  his  percentages  are  higher  than  those  of  Anderson 
is  the  employment  of  more  test  animals  and  the  injection  of 
the  cream  as  well  as  the  milk.  He  also  found  virulent 
tubercle  bacilli  in  one  of  eight  samples  of  commercially  "  pas- 
teurized" milk.  In  Manchester,  England,  7.7  per  cent  of  542 
samples  of  milk  were  found  to  be  infected.* 

Danger  Less  than  Supposed.  —  There  seems  to  be  no 
doubt  that  a  large  part  of  the  milk  consumed  in  Europe  and 
the  United  States  contains  tubercle  bacilli  in  numbers  suffi- 
cient to  cause  the  disease  in  test  animals.  It  also  seems  to 
be  certain  that  in  the  lower  animals  at  least,  particularly  in 
young  indivrduals,  the  ingestion  of  this  tuberculous  milk  will 
cause  not  only  tuberculosis  of  the  alimentary  canal,  but  will 
produce  pulmonary  disease  and  generalized  tuberculosis  also. 
It  is  probable  that  the  ingestion  of  such  milk  by  human  be- 
ings will  produce  similar  results.  There  is,  however,  consider- 
able variation  in  different  kinds  of  animals  as  regards  their 
susceptibility  to  this  sort  of  infection.  Even  in  animals  as 
susceptible  to  the  disease  as  are  guinea  pigs,  infection  by  the 
ingestion  of  milk  under  normal  conditions  is  not  very  easy. 
Thus  Schroeder  and  Cotton^  fed  132  guinea  pigs  with  tuber- 

1  Rep.  on  Health  of  Liverpool,  lOOfi,  189. 

2  Rep.  Med.  Off.  Health,  Loncl.,  1908,  00. 

3  He.ss,  Sixth  Ititernat.  Cong,  on  Tiiheie.,  Wash.,  1908,  IV,  523. 
*  Rep.  on  Health  of  Manchester,  190f5,  187. 

"  Schroeder  and  Cotton,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Circ. 
No.  83. 


INFECTION  BY  FOOD  AND  DRINK  357 

culous  milk  on  the  average  for  forty-seven  days,  and  only  1, 
which  was  fed  for  357  days,  contracted  the  disease.  This 
was  only  0.76  per  cent.  At  the  same  time  14.28  per  cent  of 
the  guinea  pigs  exposed  in  the  mangers  of  the  cows  from  which 
the  milk  was  obtained  developed  tuberculosis.  Dr.  Ver- 
ranus  Moore  writes  me  that  he  knows  of  a  small  village 
where  most  of  the  people  received  the  milk  from  a  herd 
of  cattle  that  later  was  found  to  be  extensively  diseased; 
that  is,  about  77  per  cent  reacted  to  tuberculin  and  some 
2  or  3  per  cent  showed  the  disease  on  physical  examination, 
and  a  considerable  percentage  of  the  guinea  pigs  inoculated 
with  the  mixed  milk  from  the  herd  died  of  tuberculosis. 
This  community  had  used  this  milk  for  a  number  of  years. 
After  the  facts  as  stated  above  were  ascertained  the  condi- 
tion was  changed  and  up  to  this  time  there  has  not  occurred 
a  single  case  of  recognized  tuberculosis.  Hess  *  examined  18 
children  who  a  year  previous  had  been  known  to  be  consum- 
ing tuberculous  milk.  None  of  them  showed  any  visible  signs 
of  tuberculosis,  though  4  reacted  to  the  tuberculin  test.  Of 
100  children  at  Randalls  Island,  N.  Y.,  fed  on  milk  from 
tuberculous  cows,  none  developed  the  disease.^  A  recent 
note,^  which  I  have  not  had  the  opportunity  to  verify,  gives 
the  results  of  some  observations  made  by  Weber  of  the  Ger- 
man Imperial  Health  Office  on  the  use  of  tuberculous  milk. 
From  January,  1905,  to  April,  1908,  69  cows  with  tuberculosis 
of  the  udder  were  kept  under  observation,  the  milk  from 
which  was  consumed  raw  by  360  persons,  of  whom  159 
were  children.  Of  these,  5,  of  whom  2  were  between  1 
and  2  years  of  age,  were  "  indubitably  infected  with  tuber- 
culosis through  the  use  of  the  milk."  The  children  had 
taken  the  milk  of  these  cows  from  one  to  one  and  a  half 
years.  In  both  cases  the  milk  was  used  raw  by  all  the  mem- 
bers of  the  family,  the  parents  and  several  children;  all  these 

1  Hess,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1014. 

2  Park,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  156. 
»  J.  Am.  M.  Ass.,  Chicago,  1910,  LIX,  886. 


358       THE  SOURCES  AND  MODES  OF  INFECTION 

people  remained  healthy.  In  the  sick  children  there  was 
merely  an  affection  of  the  cervical  glands  in  which  tubercle 
bacilli  of  the  typus  hovinus  were  demonstrated  by  bacteri- 
ological tests.  There  were  no  other  symptoms.  Whitla/ 
however,  reports  an  instance  where  of  150  children  fed  on 
milk  known  to  be  tuberculous,  15  contracted  the  disease. 

Percentage  Due  to  Bovine  Infection.  —  It  has  thus  far 
been  shown  merely  that  human  beings  may  contract  tuber- 
culosis by  drinking  the  milk  of  tuberculous  animals.  It  re- 
mains to  determine,  if  possible,  how  great  this  danger  really 
is.  Various  attempts  have  been  made  to  estimate  this.  It 
has  been  assumed  by  some  that  intestinal  tuberculosis,  and 
to  some  extent  generalized  tuberculosis  without  preponderant 
pulmonary  involvement,  is  indicative  of  infection  by  ingesta, 
and  presumably  by  milk.  The  fact  that  these  types  of  the 
disease  are  more  common  in  children,  of  whose  diet  milk 
forms  a  relatively  large  part,  has  been  thought  to  lend  color 
to  this  view.  It  is  not  improbable,  however,  that  the  dif- 
ferent form  which  the  disease  presents  in  early  life  may  be 
due  to  the  characteristics  of  the  age  rather  than  to  the  mode 
of  infection.  Children  certainly  consume  a  relatively  large 
amount  of  milk,  but  tuberculosis  is  not  so  common  among 
them  as  among  adults.  In  Providence  only  about  15  per  cent 
of  the  tuberculosis  is  in  children  under  five  years  of  age,  and 
only  about  4  per  cent  of  the  tuberculosis  death  rate  is  attrib- 
uted to  abdominal  tuberculosis.  In  the  registration  area  of 
the  United  States  abdominal  tuberculosis  accounts  for  about 
3.5  per  cent  of  all  deaths  from  this  disease.  This  form  of 
tuberculosis  appears  to  be  much  more  common  in  England.^ 
But  careful  observers  find  that  contact  with  other  cases  is 
probably  responsible  for  a  large  proportion  of  tuberculosis  in 
children.  Park  "'  states  that  of  100  cases  of  glandular  and 
bone  tuberculosis  in  St.  Mary's  Hospital,  New  York,  44  per 

•  Whitla,  Lancet,  Lond.,  1908,  II,  135. 

'  Bovainl,  Sixtli  Intomnt.  Coiif>;.  on  TuIkto.,  Wash.,  1908,  II,  446. 

'  Park,  Sixtli  liitenmt.  Confjr,  on  Tubcrc,  Wusli.,  1908,  I,  157. 


INFECTION  BY  FOOD  AND   DRINK  359 

cent  had  been  in  close  contact  with  tuberculous  cases. 
LaFetra^  found  40.4  per  cent  of  131  cases  of  tuberculosis  in 
infants,  probably  due  to  family  infection.  Comby  ^  considers 
family  infection  of  prime  importance  in  the  tuberculosis  of 
children.  Floyd  and  Bowditch '  found  that  679  of  1000 
tuberculous  children  had  been  in  contact  with  the  disease  in 
their  homes.  Approaching  the  subject  in  another  way,  they 
found  signs  of  the  disease  in  66  per  cent  of  746  children  living 
in  tuberculous  families  among  the  poor.  Miller  and  Wood- 
ruff* found  the  same  true  in  51  per  cent  of  150  children,  and 
Sacks  ^  in  53  per  cent  of  322  children. 

While  there  seems  to  be  no  doubt  that  tubercle  bacilli  may 
remain  latent  in  the  body  for  some  time,  there  are  very  few 
who  accept  von  Behring's  view  that  most  human  tubercu- 
losis is  acquired  in  childhood  from  drinking  tuberculous  cows' 
milk.  As  greatly  discrediting  von  Behring's  theory  may  be 
mentioned  the  investigations  of  Speck,*'  who  found  that  of 
8010  cases  of  tuberculosis  only  27  per  cent  had  been  fed  on 
cows'  milk  in  infancy.  Von  Ruck^  found  that  certainly  not 
over  25  per  cent,  and  possibly  not  over  10  per  cent,  had  been 
brought  up  on  cows'  milk.  Flick ^  obtained  similar  evidence 
at  the  Phipps  Institute  in  Philadelphia.  Hej^mann^  says 
that  in  Christiania,  where  nearly  all  the  infants  are  nursed, 
tuberculosis  is  more  common  than  in  Bavaria,  where  artificial 
feeding  is  very  common,  and  that  in  Prague,  where  nearly  all 

1  LaFetra,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  II,  361. 

2  Comby,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  II,  503. 
'  Floyd  and  Bowditch,  Boston  M.  &  S.  J.,  1908,  CLIX,  783. 

*  Miller  and  Woodruff,  Sixth  Internat.  Cong,  on  Tuberc,  Wash., 
1908,  II,  487. 

'  Sacks,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  II,  479. 
«  Speck,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1904,  XLVIII,27. 
'  Von  Ruck,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  1350. 

*  Flick,  Report  of  Henry  Phipps  Inst.  Study  .  .  .  Tuberculosis, 
Phila.,  1906,  IV,  49. 

*  Heymann,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1904, 
XLVIII,  45. 


360       THE  SOURCES  AND   MODES  OF  INFECTION 

babies  are  breast  fed,  the  tuberculosis  death  rate  is  as  high 
as  in  any  city  in  Europe.  I  am  incHned  to  the  opinion  that 
such  epidemiological  facts  as  we  have  indicate  that  children 
are  more  susceptible  to  the  human  than  to  the  bovine  type 
of  the  disease,  and  there  seems  to  be  as  much  clinical  evidence 
that  the  tuberculosis  of  childhood  is  due  to  family  infection 
as  is  the  tuberculosis  of  adult  life. 

Instances  of  Milk  Infection.  —  Instances  are  not  rarely 
reported  in  which  there  is  considerable  evidence  of  the  pro- 
duction of  tuberculosis  in  children  by  the  use  of  milk  from 
tuberculous  animals.  One  of  the  most  convincing  is  that 
narrated  by  Adams  of  Aberdeen  and  summarized  by  Hess.^ 
Two  children  of  a  farm  laborer  died  of  tuberculous  meningitis 
in  January  and  March  of  1907.  There  was  no  known  expo- 
sure to  the  disease  except  the  use  of  milk  from  a  cow  with 
tuberculosis  of  the  udder.  Bacilli  identical  in  type  with  those 
found  in  the  cow  were  recovered  from  the  cerebro-spinal  fluid 
of  one  of  the  children.  Most  of  the  cases  reported  are  not 
so  convincing  as  this,  and  in  many  the  evidence  is  decidedly 
weak  and  would  not  stand  critical  examination.  The  evidence 
afforded  by  these  cases  is  not  of  much  value,  for  though  some 
of  the  cases  are  doubtless  caused  in  the  manner  alleged,  they 
merely  indicate  what  is  also  suggested  by  animal  experiments, 
— the  possibility  of  human  infection  from  milk.  An  estima- 
tion of  the  extent  of  this  dang(>r  must  be  made  in  other  ways. 

Proportion  of  Human  and  Bovine  Types.  —  Since  the  sig- 
nificance of  Theobald  Smith's  discovery  of  the  difference 
between  the  bovine  and  human  types  of  the  tubercle  bacillus 
has  been  recognized,  the  relative  frequency  of  the  two  types 
in  human  beings  has  been  used  as  a  measure  of  the  impor- 
tance of  milk  infection,  for  it  is  conceded  that  it  is  through 
milk  almost  exclusively  that  bovine  tuberculosis  is  trans- 
mitted to  human  beings.  Much  care  and  labor  are  involved 
in  the  differentiation  of  the  two  types,  but  the  number  of 
observations  made  is  considerable,  among  which  those  of  the 
»  Hess,  J.  Am.  M.  Abs.,  Chicago,  1909,  LII,  1015. 


INFECTION  BY  FOOD  AND  DRINK  361 

German  and  British  commissions  are  notable.  IMoss^  sum- 
marizes the  cases  previously  reported.  In  all  there  had  been 
306  cases  investigated,  in  63,  or  about  20  per  cent,  of  which 
bovine  bacilli  were  found.  But  it  must  not  be  inferred  from 
this  that  20  per  cent  of  all  cases  of  human  tuberculosis  would 
present  this  type.  With  the  exception  of  54  cases  in  adults 
studied  by  the  German  commission,  most  of  the  cases  have 
been  children  with  the  intestinal  or  glandular  forms  of  the 
disease.  In  the  54  adults  no  bovine  bacilli  were  found.  The 
bovine  type  of  bacillus  has  rarely  been  found  in  pulmonary 
tuberculosis,  even  among  children.  It  may  perhaps  be  in- 
ferred that  25  per  cent  of  bone  and  glandular  tuberculosis  in 
children  is  due  to  the  bovine  bacillus.  But  Tendeloo^  calls 
attention  to  the  fact  that  if  the  bovine  type  of  bacillus  is  a 
permanent  one,  —  and  unless  it  is  these  observations  are  of 
little  value,  —  the  above  figures  are  probably  misleading,  for 
the  bovine  bacillus  if  permanent  will  be  transmitted  from 
man  to  man  and  does  not  always  indicate  a  bovine  origin. 
As  only  about  15  per  cent  of  the  tuberculosis  in  the  United 
States  is  of  the  form  in  which  the  bovine  bacillus  is  found, 
and  as  only  about  25  per  cent  of  the  cases  show  this  type  of 
bacillus,  we  are  justified,  using  the  type  as  a  test,  in  assuming 
that  only  about  5  per  cent  of  our  tuberculosis  is  derived  from 
bovine  sources.  But  this,  while  a  small  percentage,  would 
amount  to  almost  2500  deaths  annually  in  the  registration 
area  of  the  United  States,  —  certainly  a  number  which  ought 
to  be  considered. 

Epidemiological  Evidence.  —  It  seems  to  be  a  fact  that 
tuberculosis,  even  those  forms  of  the  disease  which  are  gen- 
erally supposed  to  be  caused  by  milk,  is  not  appreciably  less 
in  those  parts  of  the  world  where  cows'  milk  is  little  used,  or 
where  it  is  usually  sterilized,  or  where  there  is  little  tubercu- 
losis among  cattle.     Kitasato^  says  that  there  is  very  little 

1  Moss,  Johns  Hopkins  Hosp.  Bull.,  1909,  XX,  39. 
*  Tendeloo,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  87. 
^  Kitasato,    Ztschr.    f.    Hyg.    u.    Infectionskrankh.,    Leipz.,    1904, 
XLVIII,  471. 


362       THE  SOURCES  AND  MODES  OF  INFECTION 

tuberculosis  among  the  cattle  in  Japan,  and  so  few  cows  that 
the  daily  milk  supply  does  not  average  3  c.c.  per  capita,  yet 
nearly  8  per  cent  of  all  deaths  are  due  to  tuberculosis,  and  in 
a  series  of  autopsies  17  per  cent  of  the  tuberculosis  cases  were 
under  eighteen  years  of  age,  and  10  per  cent  of  the  cases 
showed  primary  intestinal  infection.  Cobb  says  that  substan- 
tially the  same  conditions  prevail  in  China.  According  to 
Heymann^  tuberculosis  is  very  common  in  Greenland,  where 
no  cows'  milk  is  used.  Fisch^  states  that  on  the  Gold  Coast 
no  milk  is  used,  yet  12  per  cent  of  the  sick  have  tuberculosis. 
Tuberculosis  prevails  as  extensively  in  Cuba  as  in  the  United 
States,  but  Dr.  Guiteras  tells  me  that  milk  is  practically 
never  used  without  scalding,  and  tuberculosis  is  comparatively 
rare  among  cattle.  If,  as  appears  from  a  study  of  the  relative 
prevalence  of  the  two  types  of  bacilli,  less  than  5  per  cent  of 
k\l  tuberculosis  is  due  to  cows'  milk,  the  entire  elimination  of 
this  factor  would  not,  as,  from  the  data  furnished  by  Japan, 
Cuba,  and  other  places,  it  appears  that  it  does  not,  have  any 
appreciable  effect  on  the  death  rate  from  this  disease.  The 
total  elimination  of  bovine  tuberculosis,  so  far  from  "stamp- 
ing out  the  great  white  plague,"  as  some  assert,  would  prob- 
ably not  make  any  noticeable  difference  in  the  tuberculosis 
death  rate.  Nevertheless  it  appc^ars  from  present  evidence 
that  in  the  aggregate  a  large  number  of  deaths  are  due  to 
this  cause,  and  if  there  is  any  practical  method  of  reducing 
this  cause  of  death,  effort  should  be  made  to  appl}^  it. 

Protection  against  Tuberculous  Milk.  —  Various  ways  are 
suggested  for  eliminating  this  danger  from  milk.  Among 
these  is  the  heating  of  milk  to  a  sufli(;ient  temperature  to  kill 
tubercle  bacilli  as  well  as  typhoid  bacilli  and  other  pathogenic 
organisms.  Some  have  urged  compulsory  pasteurization  by 
dealers,  and  this  practice  is,  without  any  legislation,  making 
rapid  progress  in  cities.     But,  as  is  shown  l)y  Hess  in  New 

•  Iloym.'irui,  Ztsclir.  f.  Hy^-  ".  Irifcc(i()n,sl<r;uikli.,  L(>ipz.,  1904, 
XLVIII,  45. 

'  Fisch,  Cor.-Hl.  f.  sdiwciz.  Aorztr,  1904,  XXXIV,  7(51. 


INFECTION  BY  FOOD  AND  DRINK  363 

York,  commercial  pasteurization  does  not  always  destroy 
tubercle  bacilli,  and  the  proposition  that  commercial  pas- 
teurization be  under  the  control  of  health  officials  is  a  timely 
one.  As  has  alread}'  been  stated,  there  are  objections  to  the 
compulsory'  pasteurization  of  all  milk  sold,  hence  the  federal 
Department  of  Agriculture  ^  has  suggested  a  classification  of 
market  milk  into  • — 

First.  Certified  milk,  which  presumably  would  be  free 
from  danger  and  of  high  quality,  and  would  be  sold  at  a 
higher  price  to  those  who  desired  it. 

Second.  Inspected  milk,  which  also  should  be  from  cows 
free  from  tuberculosis,  but  which  would  not  show  so  low  a 
bacterial  count  as  the  certified  milk  and  which  could  be  sold 
for  not  much  if  any  more  than  the  next  class. 

Third.  All  milk  not  produced  under  such  rigid  inspection 
should  be  pasteurized  under  municipal  supervision. 

There  certainly  is  a  tendency,  without  any  compulsion,  for 
municipal  milk  supplies  to  become  classified  in  the  way  above 
indicated.  Another  way  of  removing  the  danger  is  for  the 
consumer  to  heat  the  milk  after  it  is  received  from  the  dealer. 
In  this  way  each  consumer  can  protect  himself  from  the  dan- 
ger of  contracting  tuberculosis,  typhoid  fever  and  similar 
diseases.  But  most  persons  will  not  do  this  unless  they  are 
induced  to  do  so  by  a  slow  process  of  education,  and  this 
education  can  scarcely  be  hastened  without  causing  an 
unreasonable  fear  of  milk,  which  will  result  in  lessening  the 
consumption  of  a  cheap,  digestible  and  nutritious  article  of 
food.  It  seems  to  me  that  what  is  needed  is  a  better  and 
more  exact  knowledge  of  the  relations  of  milk  to  disease  on 
the  part  of  health  officers  and  physicians,  from  which  ought 
to  follow  a  gradual  education  of  the  public,  but  without  an 
alarmist  propaganda,  and  then  there  will  probably  gradually 
develop  a  specialization  in  the  milk  business  to  meet  the 
necessarily  different  needs  of  different  people. 

1  U.  S.  Pub.  Health  &  Mar.  Hosp.  Sen^,  Hyg.  Lab.,  Bull.  No.  41, 
559. 


364       THE  SOURCES  AND  MODES   OF  INFECTION 

Eradication  of  Bovine  Tuberculosis.  —  Another  way  of 
dealing  with  the  tuberculous  milk  problem  is  to  strive  to  eradi- 
cate bovine  tuberculosis,  or  at  least  to  eliminate  from  herds 
of  milch  cows  all  animals  in  the  active  stage  of  the  disease. 
This  is  urged  by  many,  and  has  been  and  is  being  attempted. 
It  is  claimed  by  the  federal  and  state  departments  of  agricul- 
ture that  the  existence  of  bovine  tuberculosis  entails  great  loss 
upon  the  farmers,  and  if  this  is  true,  these  departments  should 
devise  and  urge  means  for  eliminating  the  disease,  but  the 
expense  should  be  borne  by  the  farmers  and  not  by  the  public. 
If,  however,  the  restriction  or  elimination  of  bovine  tubercu- 
losis is  urged  as  a  public  health  measure,  as  it  so  often  is,  we 
should  count  well  the  cost  before  placing  it  upon  the  general 
taxpayer.  We  ought  to  have  a  finer  sense  of  financial  per- 
spective in  sanitary  matters.  The  cost  of  efficient  measures, 
if  efficient  measures  have  yet  been  devised,  for  eliminating 
bovine  tuberculosis  will  be  enormous,  and  we  may  well  con- 
sider whether  as  good  results  from  a  public-health  standpoint 
may  not  be  secured,  say  by  pasteurizing  milk,  and  whether 
the  money  might  not  be  expended  in  other  ways  with  far 
greater  results.  It  is  very  doubtful  whether  the  expenditure 
of  $100,000  a  year  for  several  years  in  a  state  like  Massachu- 
setts would  really  result  in  stamping  out  the  disease  in  cattle; 
but  consider  how  much  such  a  sum  would  accomplish  if  spent 
in  the  establishment  of  dispensaries  and  the  employment  of 
district  nurses,  with  perhaps  $5000  to  $10,000  used  for  fur- 
ther scientific  stud}^  of  the  many  unsolved  problems  connected 
with  the  causation,  prevention  and  cure  of  the  disease. 

Tubercle  Bacilli  in  Butter.  —  From  what  is  known  of  the 
viability  of  the  tubercle  bacillus,  there  can  be  no  doubt  that 
it  will  live  for  some  time  in  butter.  Schrooder  and  Cotton^ 
carefully  investigated  the  subject  and  found  virulent  tubercle 
bacilli  in  butter  after  three  months,  and  Trask^  refers  to  a  large 

1  Sohrocdor  and  Cotton,  U.  S.  Dcpt.  Agric,  Bu.  An.  Ind.,  Circ. 
No.  127,  1898. 

2  Trask,  J.  Am.  M.  Ass.,  Chicago,  1908,  LI,  1491. 


INFECTION  BY  FOOD  AND  DRINK  365 

number  of  similar  observations.  Cases  of  tuberculosis  do  not 
seem  to  have  been  traced  to  the  consumption  of  such  butter, 
and  it  is  very  unlikely  that  they  would  be  traced  even  if  they 
occurred.  Owing  to  the  small  amounts  of  butter  consumed, 
it  is  probable  that  very  few  cases  of  tuberculosis  are  caused 
in  this  way.  Butterine  also  has  been  shown  to  be  infected 
from  the  milk,  fat  and  butter  of  which  it  is  made.*  Owing 
to  the  mode  of  making  and  the  time  occupied  in  curing 
cheese,  virulent  tubercle  bacilli  are  probably  rarely  if  ever 
found  in  it." 

Mediterranean  Fever  from  Milk.  —  Mediterranean  fever, 
which  is  an  important  disease  around  the  shores  of  the 
Mediterranean,  has  been  considered  on  a  previous  page,  and 
reference  made  to  the  brilliant  researches  of  Bruce,  Horrocks 
and  others,  who  determined  that  it  is  primarily  a  disease  of 
goats,  and  only  incidentally  transmitted  to  man  through  the 
medium  of  milk.  The  obvious  remedy  is  to  avoid  the  use  of 
goats'  milk  whenever  these  animals  are  known  to  be  infected, 
and  in  the  Malta  garrison  the  disease  has  by  this  means  been 
eliminated.  It  is  rather  surprising  that  in  view  of  the  known 
facts  the  United  States  Department  of  Agriculture  should  in 
1905  have  imported  a  large  number  of  goats  from  Malta, 
but  the  importation  resulted  in  a  complete  demonstration  of 
the  infectiousness  of  the  milk,  for  quite  a  number  of  persons  on 
the  ship,  and  one  in  America,  developed  the  fever  as  a  result 
of  drinking  the  milk.     The  goats  have  now  all  been  killed. 

Anthrax  from  Milk.  —  Experiments  have  showTi  that 
anthrax  bacilli  may  be  absorbed  through  the  intestines, 
and  they  are  found  in  the  milk  of  diseased  animals.'  In- 
stances of  this  mode  of  infection  in  man  have  been  reported, 
but  they  are  certainly  very  rare.* 

1  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  1907,  XXIV,  152. 

'  Harrison,  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  1902,  XIX,  217. 

'  Horrocks,  J.  Roy.  Army  Med.  Corps,  Lond.,  1908,  XI,  46. 

*  Teacher,  J.  Comp.  Path.  &  Therap.,  Edinb.  &  Lond.,  1906,  XIX, 
225;  Meyer,  Deutsche  med.  Wchnschr.,  1908,  XXXIV,  108;  J.  Hyg., 
Cambridge,  1909,  IX,  279,  315. 


366       THE  SOURCES  AND  MODES  OF  INFECTION 

Foot-and-Mouth  Disease.  —  Foot-and-mouth  disease  is 
said  to  be  transmitted  to  human  beings  by  means  of  milk, 
and  according  to  Salmon  such  cases  are  frequently  reported 
in  European  outbreaks/  but  none  occurred  during  the  last 
outbreak  in  Massachusetts,  perhaps  owing  to  the  fact  that 
suitable  precautions  were  taken.  An  instance  of  this  sort  of 
infection  occurred  near  Boston  in  1871.^  Kober  ^  refers  to 
other  instances  of  the  transmission  of  foot-and-mouth  disease 
by  milk. 

Rabies  from  Milk. — According  to  Kober,*  Nocard  proved 
experimentally  that  rabies  could  be  conveyed  in  milk,  and 
Burdach  infected  animals  with  the  milk  of  a  woman  sick  with 
the  disease  at  the  Pasteur  Institute.  Repetto*  was  able  to 
kill  rats  by  feeding  them  with  rabies  virus,  and  Remlinger" 
did  the  same.  Dr.  Austin  Petfers  of  Boston  writes  me  that 
"  Several  times  where  cows  have  had  rabies  I  have  had  milk 
taken  from  them  and  brought  to  the  Harvard  Medical  School. 
Rabbits  and  guinea  pigs  inoculated  with  it  have  never  devel- 
oped rabies.  From  this  I  should  say  that  there  is  very  little 
danger  of  rabies  being  carried  through  the  milk." 

Other  Animal  Disease  and  Milk. — As  regards  actinomycosis, 
botryomycosis,  tetanus,  cowpox  and  many  other  animal 
diseases,  little  or  nothing  is  known  about  their  transmission 
by  milk. 

Diarrhea  from  Milk.  —  The  diarrhea  of  infants  is  prob- 
ably not  a  sp(M'ifi(;  disease,  but  the  group  of  disturbances 
which  pass  under  this  name  are  likely  to  be  due  to  infection  by 
a  number  of  organisms,  and  perhaps  to  some  extent  to  intoxi- 
cation with  the  products  of  bacterial  growth  outside  of  the 

1  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  1902,  XIX,  405. 

2  Marion,  J.  Mass.  Ass.  Bds.  Hoalth,  Bost.,  190.3,  XIII,  11. 

3  Kohor,  Milk  in  Relation  to  Public  Health,  Senate  Doc.  No.  441, 
57th  Congress,  First  Session,  1902,  154. 

*  Kohcr,  Idem,  1.57. 

'■"  Repetto,  Compt.  rend.  Soc.  hiol.,  Paris,  1908,  LXIV,  716;  Abst. 
Am.  J.  Pill).  Hyp.,  Bost.,  1909,  XIX,  420. 

•  Remlinger,  Compt.  rend.  Soc.  de  hiol.  Par.,  1908,  LXV,  385. 


INFECTION   BY  FOOD  AND  DRINK  367 

body.  Among  the  bacteria  suspected  of  causing  diarrhea 
are  B.  coli,  B.  enteritidis  sporogenes,  B.  enteritidis  (Gartner), 
B.  dysenterioe,  B.  paratyphosus  and  Streptococcus  enteritidis. 
'  The  summer  diarrheas  are  confined  principally  to  infantile 
life,  the  chief  incidence  falling  on  the  last  half  of  the  first 
year.  According  to  Newsholme^  they  are  associated  with  a 
deficient  rainfall,  and  their  dependence  upon  a  high  tempera- 
ture is  particularly  marked.  A  very  large  proportion  of  the 
deaths  occur  during  the  hot  summer  months,  and  the  hotter 
the  season,  as  a  general  thing,  the  higher  the  mortality.  The 
relation  between  temperature  and  this  disease  is  probably 
more  or  less  indirect,  and  at  present  is  not  well  understood. 
Another  marked  characteristic  of  the  summer  diarrheas  is 
that  they  are  intimatelj'  associated  with  the  mode  of  feeding. 
Breast-fed  infants  are  very  little  affected,  while  artificially 
fed  infants  suffer  severely.  As  the  artificial  food  of  infants 
is  chiefly  cows'  milk,  and  as  these  diseases  appear  to  be  of 
bacterial  origin,  and  as  the  growth  of  bacteria  in  milk  is 
enormously  facilitated  by  hot  summer  weather,  it  is  generally 
assumed  that  diarrhea  is  due  to  the  growth  of  infective  organ- 
isms in  the  milk.  Some,  however,  doubt  the  validity  of 
this  assumption.  Liefmann"  considers  that  artificial  feeding 
causes  disturbances  of  digestion  and  nutrition,  and  that  these 
lay  the  foundation  and  open  the  way  for  new  and  injuri- 
ous factors.  The  latter  are  mostly  bacterial,  and  the  bacteria 
effect  an  entrance  into  the  child's  body  in  various  ways, 
usually  by  contact  infection,  and  not  so  often  by  milk  as  has 
been  commonly  supposed.  He  says  that  the  use  of  sterilized 
milk  is  disappointing,  which  indicates  that  milk  is  not  the 
chief  vehicle  of  the  infection. 

Epidemiological  Studies.  —  In  1901-02  a  very  valuable 
series  of  observations  was  undertaken  in  New  York  by 
Park  and  Holt,  under  the  auspices  of  the  Rockefeller  Insti- 

1  Newsholme,  Pub.  Health,  Lond.,  1899-1900,  XII,  139. 
^  Liefmann,   Ztschr.   f.   Hyg.  u.   Infectionskrankh.,  Leipz.,  1908-09, 
LXII,  199;  Abst.  Pub.  Health,  1909,  XXII,  430. 


368       THE  SOURCES  AND  MODES  OF  INFECTION 

tute.'  It  appeared  to  these  observers  that  lack  of  care  in  the 
feeding  and  general  management  of  the  babies  had  more  to  do 
with  the  development  of  diarrhea  than  had  the  character  of 
the  milk.  It  is  true  that  exceptionally  dirty  store  milk  gave 
worse  results  than  any  other,  but  the  users  of  this  milk  were 
poorer  and  dirtier  and  gave  less  intelligent  care  to  their 
children.  A  rather  limited  number  of  children  were  fed  on 
fairly  good  milk  raw,  and  another  group  on  the  same  milk 
pasteurized,  other  conditions  being  nearly  the  same.  Those 
on  pasteurized  milk  had  much  less  diarrhea,  but  the  authors 
state  that  a  considerable  percentage  do  quite  as  well  on  raw 
milk.  Condensed  milk  was  found  to  be  associated  with  a 
large  percentage  of  diarrheal  cases.  Intelligent  care  and  feed- 
ing seem  to  the  authors  more  important  than  the  character 
of  the  milk.  They  also  consider  the  infection  of  the  milk  in 
the  home  or  store  as  a  very  important  factor.  Breast-fed 
babies  are  not  immune  to  diarrhea,  and  Newsholme,^  in  a 
very  careful  study  of  the  subject  at  Brighton,  found  that  6.6 
per  cent  of  the  deaths  from  diarrhea  were  in  breast-fed  infants, 
who  almost  certainly  could  not  have  been  infected  by  the 
milk.  Newsholme  pertinently  asks  why,  if  these  cases  were 
not  due  to  milk,  should  it  be  assumed  that  all  the  artificially 
fed  infants  who  succumbed  to  diarrhea  met  their  death  because 
of  milk  contamination.  From  a  study  of  the  kinds  of  milk  used 
in  Brighton  it  was  found  that  more  diarrhea  was  associated 
with  the  use  of  condensed  milk  than  with  that  of  any 
other.  Similar  results  from  the  use  of  condensed  milk  were 
found  by  Richards  in  the  neighboring  city  of  Croydon,"^  and 
by  Sandilands  in  Finsbury,  London,'*  and  their  findings  do 
not  differ  materially  from  those  of  Park  and  Holt.  In  the 
English  cities  a  very  good  brand  of  condensed  milk,  viz. 
Nestles',  was  the  one  chiefly  employed,  and  Sandilands  found 

'  Med.  News,  N.  Y.,  1903,  LXXXIII,  1066. 
2  Newsholme,  J.  Ilyu;.,  Cambridse,  19()t>,  VI,  139. 
'  Kep.  Med.  Off.  lleiilth,  Croydon,  1901,  1908. 
*  Sandilands,  J.  Ilyg.,  Cambridge,  1900,  VI,  77. 


INFECTION  BY  FOOD  AND  DRINK  369 

it  very  free  from  bacteria.  He  also  states  that  this  condensed 
milk  is  collected  and  put  up  in  Switzerland  in  such  a  manner 
as  to  make  infection  during  the  process  much  less  likely  than 
in  ordinary  market  milk.  All  the  writers  above  referred  to 
consider  that  these  facts  indicate  that  the  infective  material 
of  infantile  diarrhea  gets  into  the  milk  and  other  food  to  a 
large  extent  in  the  home.  Newsholme  especially  insists  on 
this,  and  he  attributes  not  a  little  to  direct  contact.  Tomp- 
kins/ from  a  study  of  the  very  local  distribution  of  the  disease 
in  Leicester,  concluded  that  it  must  have  its  source  in  local 
conditions.  Robertson  and  Niven,  from  a  study  of  cases  in 
their  respective  cities  of  Birmingham  and  Manchester,  believe 
that  the  infection  takes  place  in  the  city  chiefly,  either  by 
direct  infection  or  through  the  milk. 

Explosive  Outbreaks  of  Diarrhea.  —  Sometimes  what 
appear  to  be  explosive  milk-borne  outbreaks  of  diarrhea 
occur.  Several  such  are  referred  to  by  Newman.^  Recently 
a  very  interesting  outbreak  of  this  kind  has  been  reported 
by  Hay.^  Various  bacteria,  such  as  B.  coli,  B.  enieritidis 
sporogenes  and  B.  enteritidis  of  Gartner,  have  been  isolated 
from  the  milk  in  such  cases  and  also  from  the  evacuations 
of  the  patients.  It  is  uncertain  whether  such  outbreaks  have 
any  connection  with  ordinary  summer  diarrhea,  though  that 
they  have  is  the  view  of  Delepine,*  and  he  believes  that  the 
contamination  of  milk  usually  takes  place  at  the  farm. 

Prevention  of  Diarrhea.  —  It  appears,  then,  that  we  have 
very  little  accurate  knowledge  as  to  the  causation  of  infantile 
diarrhea.  It  certainly  has  some  intimate  relation  to  the  diet, 
but  exactly  what  is  not  known.  We  do  know,  however,  that 
the  most  efficient  means  we  have  of  combating  it  is  correct 
feeding.  Breast  feeding  is  far  superior  to  anything  else,  but 
good  success  can  be  obtained  with  the  careful  and  scientific 

1  Tompkins,  Brit.  M.  J.,  Lond.,  1889,  II,  180. 
*  Newman,  Infant  Mortality,  Lond.,  1906,  170. 

3  Hay,  Pub.  Health,  Lond.,  1910,  XXIII,  180. 

4  Delepine,  J.  Hyg.,  Cambridge,  1903,  III,  89. 


370        THE  SOURCES  AND   MODES  OF  INFECTION 

use  of  good  cows'  milk.  Pasteurized  milk  appears  to  be  better 
than  dirty  raw  milk  of  high  bacterial  count,  but  there  does 
not  seem  to  be  any  definite  connection  between  the  disease 
and  an  increasing  bacterial  content.  The  longer  milk  re- 
mains exposed  in  shops  and  houses,  the  more  dangerous  it 
seems  to  be.  Almost  all  who  have  had  to  do  with  modern 
milk  stations,  either  those  using  pasteurized  milk  or  those 
dispensing  clean  raw  milk,  agree  that  the  larger  part  of  the 
resulting  good  is  due  to  the  education  of  the  mother  in 
the  care  of  her  child.  The  chief  thing,  then,  is  to  teach  the 
mothers  how  to  modify,  keep  and  feed  milk.  It  is  of  impor- 
tance, too,  that  the  mothers  should  be  enabled  to  get  fairly 
clean  and  fresh  milk.  In  some  cities  it  is  doubtless  necessary 
to  establish  milk  stations  for  this  purpose,  which  dispense 
either  pasteurized  milk,  or  preferably  clean  raw  milk.  In 
Providence  stations  were  found  to  be  unnecessary,  as  there  is 
no  part  of  the  city  in  which  it  is  not  possible  to  get  18  to  24 
hours'  old  milk  with  less  than  50,000  l)acteria  perc.c,  and  a 
number  of  dealers  furnish  milk  below  10,000.  This  milk  is 
sold  by  the  producer  in  glass  bottles  and  at  the  ordinary 
market  price.  The  milk  is  by  no  means  equal  to  certified 
milk,  but  the  observations  of  Park  and  Holt,  and  our  expe- 
rience in  Providence,  seem  to  show  that  milk  of  the  grade 
above  indicated  is  ordinarily  as  little  likel^y  to  cause  infantile 
diarrhea  as  is  certified  milk.  Only  a  small  amount  of  the  milk 
supply  of  a  city  is  used  for  feeding  infants,  and  it  seems  un- 
necessary to  insist  on  a  high  grade  of  expensive  milk  for  all 
consumers.  At  present  it  is  more  economical  to  bring  the 
existing  good  supplies  to  the  knowledge  of  the  mothers 
througii  i)hysicians,  the  health  department,  district  nurses 
and  milk  stations.  In  cities  up  to  200,000  or  300,000  it  is 
probable  that  enough  dealers  (!an  be  found  to  supply  the 
necessary  dciiKind  for  a  good  though  not  certified  milk. 


INFECTION  BY  FOOD  AND  DRINK  371 

Infection  by  Meat. 

Inspection  of  meat  is  considered  by  the  public  a  matter  of 
the  greatest  importance,  but  concerning  many  forms  of  meat 
infection  we  have  httle  definite  knowledge,  and  the  danger  of 
others  has  been  greatly  exaggerated,  not  only  by  the  public, 
but  also  by  physicians  and  health  officials.  Various  animal 
parasites,  such  as  tapeworms  and  trichinae,  are  derived  from 
the  lower  animals  through  the  use  of  their  flesh  as  food,  but 
a  consideration  of  these  is  be^-ond  our  present  purpose.  One 
of  these  animal  parasites,  the  trichina,  is  quite  common  in 
pork,  and  a  considerable  number  of  deaths  are  caused  by  it 
each  year. 

Food  Poisonings.  —  What  are  commonly  called  food  poi- 
sonings, when  resulting  from  eating  meat,  are  due  to  two 
general  causes.  One  class  is  the  result  of  the  action  of  various 
kinds  of  putrefactive  organisms  which  infect  the  food  after 
slaughter.  These  cases  we  need  not  consider.  Another  class 
results  from  infection  of  the  flesh  during  the  life  of  the  animal, 
and  is  due,  so  far  as  known,  to  various  members  of  the  colon 
group,  such  as  B.  -paratyphosus,  B.  enteritidis  (Gartner)  and 
B.  morbificans.  In  many  instances  this  unwholesome  meat  is 
derived  from  diseased  animals,  usually  showing  some  sort  of 
enteritis  or  septic  infection.  That  the  infection  is  always 
derived  from  diseased  animals  seems  unlikely,  for  several 
observers  have  found  in  healthy  animals  the  bacteria  which 
are  believed  to  be  the  cause. ^  Savage,^  however,  was  un- 
able to  isolate  B.  enteritidis  (Gartner)  from  the  intestines  of 
23  healthy  animals  which  he  carefully  studied.  But  from 
what  is  known  of  the  relations  of  this  group  of  bacteria  to 
human  beings  we  should  expect  to  find  them  occasionally  in 
healthy  animals,  convalescents  and  carriers.  Unfortunately 
the  toxins  produced  by  these  bacteria  are  not  always  de- 

1  Bolduan,  Food  Poisoning,  New  York,  1909,  33. 

2  Savage,  Rep.  Med.  Off.  of  Local  Gov.  Bd.,  1906-07,  XXXVI,  253; 
1907-08,  XXXVII,  425. 


372       THE  SOURCES  AND  MODES  OF  INFECTIOX 

stroyed  by  heat,  so  that  while  cooking  may  kill  the  bacteria, 
cooked  meat,  which  has  been  the  seat  of  bacterial  growth, 
has  been  known  to  cause  sharp  outbreaks  characterized  by 
acute  gastrointestinal  symptoms.  If  living  bacteria  of  this 
group  are  present,  infection  with  them  may  result,  causing  a 
slow  after  development  of  symptoms  somewhat  akin  to  those 
of  typhoid  fever.  The  cooking  of  meat  cannot  be  relied  upon 
wholly  to  prevent  sickness  arising  from  this  sort  of  food 
infection.  Government  inspection  is  suggested  as  the  only 
method  by  which  these  diseases  can  be  prevented.  If,  how- 
ever, bacilli  are  found  in  healthy  animals,  it  is  questionable 
whether  any  amount  of  inspection  would  entirely  eliminate 
the  danger.  How  great  the  danger  is  it  is  difficult  to  deter- 
mine. A  good  many  outbreaks  have  been  reported  in  Ger- 
many, aggregating  thousands  of  cases,  and  reports  come  not 
rarely  from  England.  No  data  are  available  for  the  United 
States.  For  several  years  I  have  been  on  the  lookout  for 
the  reports  of  such  cases  in  the  medical  press  and  in  the 
"Index  Medicus,"and  one  year  I  employ-ed  a  press-clipping 
bureau  to  secure  cuttings  from  the  lay  press,  but  I  have 
notes  of  scarcely  more  than  a  dozen  outbreaks.  Doubtless 
others  occurred,  but  they  cannot  have  been  very  numerous. 
A  good  many  reports  of  instances  of  "  ptomaine  poisoning  " 
find  their  way  into  the  newspapers,  which  prove  on  investi- 
gation to  have  no  basis  in  fact. 

Meat  and  Tuberculosis.  —  In  the  public  mind  the  fear  of 
contracting  tuberculosis  by  eating  meat  is  very  considerable, 
and  public  sentiment  is  sufficient  to  support  very  stringent 
regulation  of  the  sale  of  meat  from  diseased  animals.  Yet 
it  does  not  appear  that  there  is  a  single  recorded  instance  of 
the  transmission  of  disease  in  this  way.  And  we  should 
expect  that  if  such  were  possible  it  would  be  exceedingly  rare. 
Tubercle  bacilli  have  their  habitat  in  lungs,  liver,  intestines, 
glands  and  other  viscera,  and  not  usually  in  the  muscle  or 
fat.  The  tubercle  bacillus  is  easily  killed  by  heat,  and  very 
little  of  this  class  of  food  is  eaten  without  cooking.     Smoked 


II 


INFECTION  BY  FOOD  AND  DRINK  '    373 

beef  and  ham  are  occasionally  eaten  without  cooking,  but  even 
then  considerable  time  is  consumed  in  the  process  of  corning 
and  smoking,  and  in  the  rare  cases  in  which  a  few  bacilli 
are  contained  in  the  meat  they  are  likely  to  have  lost  most 
of  their  virulence.  As  for  the  viscera,  if  they  are  used  at  all 
for  food  they  are  generally  pretty  well  cooked.  Cornet  states 
that  Schottelius  studied  the  use  of  meat  from  tuberculous 
animals  in  Wiirzburg,  and  could  not  find  a  case  of  the  disease, 
although  the  meat  was  eaten  in  every  form.  It  has  been 
said  that  while  tuberculosis  has  been  decreasing  the  consump- 
tion of  meat  has  been  increasing;  and  this  is  certainly  an 
indication  that  the  use  of  meat  cannot  be  a  factor  of  any 
great  moment  in  the  causation  of  the  disease.  At  the  most 
it  is  scarcely  possible  for  the  disease  to  be  derived  from  this 
source  except  in  rare  instances. 

Conclusions.  —  The  diseases  which  it  is  alleged  may  be 
transmitted  by  flesh  foods  are  those  caused  by  animal  para- 
sites, of  which  trichinosis  is  the  most  important,  diseased 
conditions  produced  by  the  colon  group  of  bacilli,  and  tuber- 
culosis. The  latter  is  a  negligible  quantity,  the  second  group 
probably  causes  very  few  deaths  in  this  country,  while  trichi- 
nosis is  doubtless  the  most  important  disease  transmitted  in 
this  manner. 

Federal  Control.  —  The  federal  government  has  instituted 
an  expensive  meat-inspection  service,  ostensibly  to  guard  the 
health  of  the  public,  but  as  trichinosis,  the  most  common  and 
serious  of  the  animal  diseases,  though  it  is  very  rare  in 
man,  is  ignored,  it  is  suspected  that  the  system  was  insti- 
tuted by  Congress  as  the  result  of  an  ill-informed  though 
popular  demand.  Filthy  conditions  in  the  slaughterhouses, 
and  the  killing  of  diseased  animals,  though  their  flesh  may 
not  be  injurious  to  health,  are  shocking  to  the  aesthetic  sense 
and  the  public  demands  reform.  Including  the  expense  of 
inspection  and  the  value  of  the  meats  condemned,  the  cost 
to  the  country  is  $5,000,000  or  $6,000,000  per  annum.  It  is 
true  that  the  conditions  of  labor  in  the  great  packinghouses 


374       THE  SOURCES  AND  MODES  OF  INFECTION 

have  been  improved,  and  that  cleanlier  methods  of  handling 
meat  have  been  enforced,  but  it  is  doubtful  whether  any  sick- 
ness among  consumers  has  been  prevented.  I  cannot  help 
thinking  how  much  ultimate  good  might  have  accrued  if  a 
tenth  of  the  sum  spent  in  meat  inspection  had  been  devoted 
to  the  systematic  stud.y  of  the  many  unsolved  problems  of 
sanitation,  such  as,  for  instance,  the  danger  from  fomites,  the 
part  played  by  air  in  the  spread  of  disease,  the  causes  of 
the  decline  of  tuberculosis  and  the  mode  of  extension  of  the 
disease,  the  relation  of  food  to  health,  the  causes  of  infantile 
diarrhea,  the  relation  of  water  supplies  to  the  general  health, 
or  the  meaning  of  bad  air  and  its  effect  on  health. 

Infection  by  Shellfish. 

Oysters.  —  Since  oysters  and  other  shellfish  are  often 
eaten  raw,  and  often  live  in  sewage-polluted  waters,  they 
might  be  suspected,  and  indeed  were  suspected  by  Sir  Charles 
Cameron  as  long  ago  as  1880,  of  being  the  cause  of  typhoid 
fever,  and  in  1893  Thorne  suggested  that  the  sporadic  cases 
of  cholera  which  appeared  here  and  there  in  England  were 
due  to  the  eating  of  raw  shellfish  infected  at  the  mouth  of 
the  Humber.  The  first  demonstration  of  the  relation  of  shell- 
fish to  disease  was  by  Conn.^  He  showed  that  23  of  100 
students  who  went  to  a  certain  banquet  developed  typhoid 
fever,  probably  as  a  result  of  eating  oyst(n-s.  Of  those  who  did 
not  eat  raw  oysters  none  were  sick,  and  one  man  who  did  not 
go  to  the  banquet  ate  oysters  at  the  dealers'  and  also  was  sick. 
The  oysters  had  been  kept  about  300  foet  from  a  drain  leading 
from  a  house  where  there  was  typhoid  fever.  Similar  out- 
breaks have  been  reported  by  Chantemesse,^  Mosny,^  Chatin,'* 

»  Conn,  Rep.  St.  Bd.  Health,  Connect.,  1895,  253;  Med.  Rec,  N.  Y., 
1894,  XLVI,  743. 

»  Chantemesse,  Bull.  Acad,  de  med.,  Par.,  1896,  3  a.  XXXV,  588, 
724. 

'  Mosny,  R(!v.  d'liyK.,  1900. 

*  Chatin,  Seniaiue  mod,  1897,  XVII,  91. 


INFECTION  BY   FOOD   AND   DRINK  375 

Thresh  and  Wood,'  a  committee  which  studied  the  subject 
at  Atlantic  City,^  Fraser,^  Soper*  and  Morse.'' 

Clams,  Mussels.  —  Clams  as  well  as  oysters  have  been 
believed  to  be  the  cause  of  outbreaks,®  and  where  mussels 
and  cockles  are  consumed  raw  in  considerable  quanti- 
ties they  are  equally  liable  to  carry  the  infecting  organ- 
isms. Three  outbreaks  in  Norwich,  England,  in  1908  were 
traced  to  mussels.^  Mussels  also  were  believed  to  be  the 
cause  of  an  outbreak  of  typhoid  fever  in  North  Ormsby,' 
and  have  been  an  important  factor  in  the  causation  of 
typhoid  fever  in  Belfast. 

Shellfish  in  English  Cities.  —  Not  only  have  shellfish  been 
shown  to  be  the  cause  of  marked  outbreaks  of  illness,  as 
just  shown,  but  they  are  strongly  believed  by  many,  espe- 
cially by  English  health  officials,  to  be  an  important  source  of 
the  ordinary  "  residual  "  typhoid  fever  occurring  in  cities. 
Newsholme®  is  especially  insistent  on  this.  A  careful  study 
of  the  matter  in  Brighton,  where  he  was  then  health  officer, 
showed  that  in  1894-96,  of  189  reported  cases  of  typhoid  fever, 
41  were  imported,  and  of  the  148  remaining,  51,  or  nearly  30 
per  cent,  had  eaten  raw  oysters  or  mussels  within  the  incuba- 
tion period  of  the  disease.  These  shellfish  all  came  from 
grounds  which  were  contaminated  with  sewage.  From  1894 
to  1902,  of  643  reported  cases  of  typhoid  fever,  158  were  due 
to  eating  oysters  and  80  to  other  shellfish,  making  in  all  about 
37  per  cent  due  to  this  cause.  Similar  observations  and  con- 
clusions may  be  found  in  the  reports  of  the  health  officers 
of  Birmingham,  Leicester,  Southend,   Manchester,  London, 

1  Thresh  and  Wood,  Lancet,  Lond.,  1902,  II,  1567. 

2  Phila.  M.  J.,  1902,  X,  634. 

3  Fraser,  Lancet,  Lond.,  1903,  I,  183. 

*  Soper,  Med.  News,  N.  Y.,  1905,  LXXXVI,  241. 

'  Morse,  Rep.  St.  Bd.  Health,  Mass.,  1900,  836. 

6  Plowright,  Brit.  M.  J.,  Lond.,  1900,  II,  681. 

'  Rep.  on  Sanitary  Condition  of  Norwich,  1908,  14. 

'  The  Medical  Officer,  1909,  II,  431. 

'  Newsholme,  J.  San.  Inst.,  Lond.,  XVII. 


376       THE  SOURCES  AND  MODES  OF  INFECTION 

Portsmouth  and  other  places.  The  typhoid  death  rate  in 
EngUsh  cities  is  low  and  health  officials  find  it  difficult  to 
account  for  the  origin  of  the  cases.  The  pollution  of  shellfish 
with  sewage  is  not  uncommon  around  the  English  and  Irish 
coasts.^  A  considerable  percentage  of  the  cases  of  typhoid 
fever  are  known  to  have  eaten  shellfish,  often  from  polluted 
sources,  within  two  to  four  weeks  of  the  date  of  attack. 
Perhaps  the  assumption  is  justifiable  that  some  of  these  cases 
at  least  are  due  to  the  shellfish.  Typhoid  fever  has  for  some 
time  been  rather  prevalent  in  Belfast,  and  a  special  commis- 
sion was  appointed  for  its  investigation.  This  commission 
believes  that  the  chief  source  of  the  disease  is  mussels  and 
cockles,  picked  up  by  the  poorer  people  along  the  sewage- 
polluted  flats.^  Mair^  states  that  in  Belfast  it  was  impossible 
to  make  a  satisfactory  canvass  of  the  number  of  mussel  users, 
either  among  the  general  population  or  among  the  typhoid 
patients.  He  bases  his  conclusions  as  to  the  part  played  by 
mussels  on  a  careful  statistical  study,  and  shows  that  the 
disease  in  Belfast  has  varied  according  to  changes  in  the 
amount  of  mussels  consumed.  He  also  shows  that  Jews  and 
the  wealthier  classes,  who  use  no  mussels,  had  little  typhoid 
fever.  Nash*  states  that  at  Southend  54  per  cent  of  the 
typhoid-fever  cases  confessed  to  the  eating  of  shellfish,  while 
only  0.4  per  cent  of  501  sick  with  other  diseases  confessed  to 
such  eating.  Since  the  consumption  of  raw  shellfish  has 
decreased,  typhoid  fever  has  decreas(Kl  also.  In  Leicester,^ 
50  per  cent  of  the  typhoid  cases  ate  mussels,  but  they  were 
used  in  only  15  per  cent  of  a  small  number  of  noninfected 
houses.     Johnston^  found  that  25.8  per  cent  of  62  persons 

1  Rep.  Med.  Off.  Loo.  Cov.  Bd.,  1S94-95,  XXIV;  Loc.  Gov.  Bd.  for 
Ireland,  Rop.  on  Shellfish  Layings,  1904. 

2  U.  S.  Pub.  Health  <k  Mar.  IIo.sp.  Serv.,  Pub.  Health  Rep.,  Wash., 
1908,  XXIII,  99.5. 

'  Proc.  Roy.  Soe.  Med.,  Lond.,  1909,  II,  Epidem.  Sect.,  187. 

*  Nu,sh,  Pub.  Health,  Lond.,  190:5-Or),  XVI,  80. 

'-  liep.  Med.  f)IT.  IleaHh,  Leicester,  1908,  31. 

"  Johnston,  The  Medical  Officer,  II,  1909,  431, 


INFECTION  BY  FOOD  AND  DRINK  377 

with  typhoid  fever  had  eaten  shellfish,  mussels  and  peri- 
winkles within  a  short  time  of  their  illness,  while  of  827 
other  persons  only  7.3  per  cent  had  eaten  them  during  the 
whole  summer.  In  the  United  States,  also,  non-epidemic  or 
"  residual  "  typhoid  has  been  attributed  to  the  use  of  raw 
oysters,  as  in  New  York.^  The  chief  reason  for  this  seems 
to  be  that  there  is  known  to  be  a  considerable  consumption 
of  sewage-infected  oysters.'  Most  of  the  beds  on  which 
oysters  are  grown  are  free  from  dangerous  pollution,  but  it 
is  quite  common  to  "  fatten,"  i.e.,  freshen  and  swell  them,  in 
estuaries  near  sewer  openings. 

Danger  Variable.  —  It  seems  reasonable  to  conclude  that 
the  danger  from  eating  sewage-infected  shellfish  is  a  real  one. 
Exactly  how  great  it  is,  is  difficult  to  determine.  In  England 
anywhere  from  15  to  50  per  cent  of  the  disease  in  cities  is 
attributed  to  eating  raw  mussels  or  oysters,  but  this  is  on  the 
supposition  that  every  typhoid  patient  who  has  recently  eaten 
raw  shellfish  derived  the  disease  from  that  source.  In  Provi- 
dence raw  oysters  are  very  popular;  they  are  consumed  in 
restaurants  in  large  numbers,  and  form  a  course  in  a  large 
proportion  of  banquets  and  dinners.  Many  oysters  are 
grown  in  the  upper  part  of  the  bay,  in  water  grossly  contami- 
nated with  sewage,  and  in  the  water  and  in  the  oysters 
colon  bacilli  are  found.  Until  within  two  or  three  years, 
numbers  of  oysters  from  clean  water  have  been  "fattened" 
near  sewer  openings,  yet  Providence  has  a  typhoid  death 
rate  less  than  half  that  of  the  average  American  city.  Oys- 
ters are  not  eaten  to  any  extent  in  August,  when  typhoid 
fever  begins  to  increase,  and  they  are  largely  consumed  in 
the  winter  and  spring,  when  there  is  little  of  the  disease. 
During  the  years  1902-05,  of  263  typhoid-fever  patients  who 

1  Med.  News,  N.  Y.,  1904,  LXXXIV,  325;  1905,  LXXXV,  571. 

^  Repoct  of  U.  S.  Commissioner  of  Fisheries  for  year  ending  Jan.  30, 
19C4,  Appendix,  189;  Rep.  Dept.  Health,  City  of  N.  Y.,  1904,  I,  313; 
Rep.  St.  Bd.  Health,  New  Jersey,  1904,  226;  Rep.  Dept.  Health,  Balti- 
more, 1907,  124. 


378       THE  SOURCES  AND  MODES  OF  INFECTION 

replied  definitely  as  to  whether  they  had  eaten  oysters,  only 
26,  or  about  10  per  cent,  said  that  they  had.  Very  few  raw 
oysters  are  eaten  by  laboring  people,  but  at  present  laboring 
people  furnish  fully  their  share  of  typhoid  fever. 

While  the  amount  of  typhoid  fever  due  to  the  use  of  raw 
shellfish  is  not  very  great,  this  danger  ought  to  be  eliminated 
entirely,  and  state  boards  of  health  should  have  the  authority 
to  forbid  the  sale  of  shellfish  from  polluted  waters. 

Crawfish  and  Typhoid  Fever.  —  Dr.  Bissell  of  Buffalo 
wrote  to  me  about  an  interesting  local  outbreak  of  typhoid 
fever  which  was  at  first  suspected  to  be  due  to  milk.  But 
further  investigation  showed  that  it  was  confined  chiefly  to 
boys,  and  that  these  boys  were  in  the  habit  of  catching  craw- 
fish from  a  lake  grossly  polluted  with  sewage.  After  par- 
tially cooking  the  crawfish  before  an  open  fire  in  the  field, 
the  boys  would  eat  them. 

Infection  by  Fried  Fish. 

In  1900,  Hamer  '  of  London  reported  outbreaks  of  typhoid 
fever  in  South wark,  Lambert  and  Kensal-town  which  seemed 
to  be  confined  in  each  case  to  the  customers  of  certain  fried- 
fish  shops.  While  the  sickness  was  believed  to  be  due  to 
the  eating  of  fish,  no  conclusion  was  reached  as  to  how  the 
fish  became  infected.  It  is  scarcely  possible  that  infection  of 
the  fish  before  cooking  should  not  be  destroyed  by  the  pro- 
cess, and  yet  it  seems  unlikely  that  handling  by  carriers  after 
infection  could  cause  such  an  outbreak. 

Infection  by  Watercress. 

In  the  summer  of  1903  there  was  a  very  considerable  out- 
break of  typhoid  fever  in  Hackney,  London.^  This  was  very 
carefully  investigates!  by  Warry,  and  he  eliminated  all  articles 
of  food  and  drink  as  sources  of  the  infection,  except  water- 
cress.    Of  tiie  110  cases  55.3  per  cent  ate  watercress  which 

»  Ilamor,  Special  Rep.  to  Med.  OfT.  H(>alt,li,  Lond.,  1900. 
2  Warry,  Rep.  Med.  Off.  Ilcallli,  Loiul.,  1903,  35. 


INFECTION  BY  FOOD  AND  DRINK  379 

grew  in  sewage-polluted  water.  An  inquiry  showed  that  the 
incidence  of  the  disease  on  watercress  eaters  was  three  times 
as  great  as  upon  those  who  did  not  eat  it. 

Infection  by  Celery. 

Morse  ^  reports  an  outbreak  of  typhoid  fever  due  to  the 
use  of  celery.  There  were  49  cases  in  an  insane  asylum. 
Nearly  all  of  these  belonged  to  the  class  of  pay  patients,  to 
whom  alone  celery  was  served.  Several  other  persons,  how- 
ever, had  access  to  the  celery  and  contracted  the  disease. 
There  were  no  cases  except  four  contact  cases  among  non- 
users  of  celery.  There  had  been  typhoid  fever  in  the  insti- 
tution some  months  before  and  the  celery  bed  had  received 
the  hospital  sewage.  The  disease  developed  soon  after  the 
celery  came  into  use. 

^  Morse,  Rep.  St.  Bd.  Health,  Mass.,  1899,  761. 


CHAPTER  VIII. 

INFECTION   BY    INSECTS. 

Importance  of  Subject.  —  The  subject-matter  of  this  chap- 
ter is  of  the  utmost  importance  in  the  practical  work  of  pre- 
ventive medicine,  and  it  is  of  equal  interest  to  the  student  of 
scientific  epidemiology.  Our  actual  knowledge  of  the  insect 
carriers  of  disease  has  all  been  acquired  during  the  last  fif- 
teen or  twenty  years,  and  marks  as  brilliant  and  successful 
an  epoch  in  the  history  of  medicine  as  did  the  phenome- 
nal development  of  bacteriology  in  the  years  immediately 
preceding. 

I  hesitate  very  much  to  discuss  the  subject  at  all,  as  most 
of  the  diseases  considered  are  essentially  tropical,  and  of 
tropical  diseases  I  have  had  no  personal  knowledge.  But 
even  we  who  dwell  in  temperate  regions  are  likely  to  meet 
with  isolated  cases  of  tropical  diseases,  or  to  suffer  from 
occasional  invasions  of  yellow  fever,  bubonic  plague  and 
relapsing  fever.  In  any  event,  it  is  important  that  both  the 
student  of  preventive  medicine  and  the  health  officer  keep 
informed  as  to  current  progress  in  this  line  of  research,  and 
ever  bear  in  mind  the  possibility  that  insects  may  play  a 
part,  at  least,  in  the  spread  of  those  diseases  with  which  he 
is  more  familiar. 

Modes  of  Transmission.  —  There  are  various  ways  in 
wiiich  disease  may  be  transmitted  by  insects.  The  most 
interesting  and  to  us  novel  manner  in  which  this  happens  is 
that  the  discovery  of  which  we  owe  to  Theobold  Smith,  in 
which  the  insect,  as  well  as  the  higher  animal,  serves  as  the 
true  host  of  the  pathogenic  organism  which  causes  the  disease. 
Most  of  the  diseases  transmitted  in  this  way  are  probably 
caused  by  animal  parasites,  usually  protozoa.     As  a  rule, 

380 


INFECTION  BY  INSECTS  381 

they  propagate  asexually  only  in  man  or  the  higher  animals, 
but  develop  sexual  forms  in  insects,  which  thus  become,  zoo- 
logically considered,  their  true  hosts,  while  man,  if  it  be  a 
human  disease,  is  the  intermediate  host.  The  insects  in  such 
instances  are  sometimes  called  biological  carriers.  In  other 
cases  the  parasites  do  not  develop  in  the  insect,  which  is  then 
merely  a  mechanical  carrier,  as  would  be  a  lancet  or  a  hypo- 
dermic syringe.  The  classification  of  insect-borne  diseases  is 
far  from  definite,  owing  to  the  present  fragmentary  condition 
of  our  knowledge.  We  will  first  consider  those  diseases  which 
appear  to  be  biologically  carried  by  insects. 

First  Proof  of  Transmission  by  Insects.  —  Although  there 
had  previously  been  suggestions  that  disease  might  be  trans- 
mitted by  insects,  the  first  definite  proof  was  the  demonstra- 
tion in  1893  by  Smith  and  Kilborne  '  of  the  development  of 
Piroplasma  higeminum  and  the  part  played  by  ticks  in  the 
transmission  of  Texas  cattle  fever.  This  discovery  did  much 
to  point  out  the  lines  on  which  experimental  work  should 
proceed.  These  authors  demonstrated  the  presence  of  the 
Piroplasma  in  the  blood  of  infected  cattle  and  in  the  ticks 
which  fed  upon  them.  They  also  showed  that  the  ticks  trans- 
mit the  germ  through  their  eggs  to  their  progeny.  The 
new  generation  of  infected  ticks  then  become  attached  to 
cattle,  and  by  their  bites  inoculate  them  and  cause  the  disease. 
It  was  demonstrated  that  there  could  be  no  infection  of  the 
fields  or  fodder,  either  b}'  the  excreta  of  cattle  or  by  dead 
ticks  or  ova.  The  living  tick  is  necessary  for  the  transmis- 
sion of  the  disease,  and  doubtless  the  Piroplasma  passes 
through  definite  phases  of  its  development  in  the  body  of  the 
tick.  Smith  and  Kilborne  showed  not  only  that  ticks  trans- 
mit this  disease,  but  also  that  it  is  transmitted  only  in  this 
way.  They  furthermore  showed  that  apparently  healthy  cat- 
tle might  be  carriers  of  the  Piroplasma,  and  therefore  in  the 
presence  of  ticks  could  cause  the  spread  of  the  disease.     Texas 

^  Smith  and  Kilborne,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Bull.  1, 
1893. 


382       THE  SOURCES  AND   MODES  OF   INFECTION 

cattle  fever,  though  of  immense  economic  importance  in  the 
cattle-raising  industry,  is  not  transmissible  to  human  beings. 
The  great  importance  of  Smith  and  Kilborne's  discovery,  from 
our  present  point  of  view,  is  the  encouragement  it  gave  to  the 
study  of  the  transmission  of  human  diseases  by  insect  agen- 
cies. Koch  has  demonstrated  a  similar  connection  between 
ticks  and  a  disease  of  cattle  in  German  East  Africa  caused  by 
another  species  of  Piroplasma,  —  P.  parvum.  Nuttall  and 
Graham-Smith  ^  have  investigated  a  similar  disease  in  dogs, 
also  transmitted  by  ticks,  and  have  described  the  devel- 
opment of  the  parasite  P.  canis.  Christophers  also  ^  has 
studied  the  development  of  this  parasite.  There  appears 
to  be  no  doubt  that  piroplasmosis  of  horses  and  sheep  is 
transmitted  by  ticks. 

Malaria. 

Discovery  of  Insect  Transmission.  —  While  Nott,'  King,* 
Laveran, '  Koch  and  others  had  suggested,  on  epidemiological 
grounds,  that  this  disease  might  be  insect  borne,  it  was  not 
until  1895  that  Ross,^  stimulated  by  the  work  of  Manson 
on  filariasis,  watched  the  development  of  the  malarial  parasite 
in  mosquitoes  which  had  been  allowed  to  bite  persons  sick 
with  the  disease.  As  Manson  had  already  shown  that  in 
filariasis  it  is  only  a  particular  species  of  mosquito  which 
can  serve  as  host  for  the  filaria,  Ross  suspected  that  the 
same  might  be  true  of  human  malaria,  and  he  finally  deter- 
mined that  it  was  only  in  individuals  of  the  genus  Anopheles 
that  the  malarial  parasite  can  develop.     Ross '  now  turned 

1  Nuttall  and  Graham-Smith,  .J.  Ilyg.,  Cambridge,  1904,  1905,  1906, 
1907. 

2  Christophers,  Rrit.  M.  .1.,  Lond.,  1907,  II,  1333. 
»  Nott,  N.  Orl.  M.  &  S.  J.,  1847-48,  IV,  563. 

*  King,  Tr.  Philos.  Soc,  Wash.,  1883. 

*  Laveran,  Le  Pahidisme,  Paris,  1891,  147. 

*  Ross,  Abst.  by  Manson,  Lancet,  Lond.,  1896,  I,  831. 

"  Ross,  Rep.  on  the  Cultivation  of  Protcosoma  Labbe  in  Grey  Mos- 
quitoes, Indian  M.  Gaz.,  Calcutta,  1898,  XXXIII,  133,  401,  448. 


INFECTION  BY  INSECTS  383 

to  the  study  of  the  malaria  of  birds  due  to  a  Proteosoma,  and 
he  demonstrated  that  the  disease  could  be  transmitted  from 
bird  to  bird  by  the  bites  of  mosquitoes.  The  parasites  of  the 
disease  are  taken  up  with  the  blood  by  the  insect  in  the  act 
of  biting,  and  after  undergoing  sexual  multiplication,  spread 
through  the  insect,  and  are  found  in  the  salivary  gland, 
whence  they  are  injected  into  the  next  bird  bitten.  Mean- 
while Grassi  in  Italy  had  come  to  the  conclusion,  from  a  study 
of  the  distribution  of  different  species  of  mosquitoes,  that 
Anopheles  was  one  of  the  forms  likely  to  transmit  the  disease. 
Bignami  had  previously  been  unsuccessful  in  transmitting 
malaria  by  the  bites  of  mosquitoes,  chiefly  because  he  experi- 
mented largely  with  Culex  instead  of  Anopheles.  Finally 
Grassi,  Bignami  and  Bastianelli  in  1899  caused  malaria  in 
human  beings  by  allowing  anopheles  mosquitoes  to  bite  them 
some  days  after  they  had  bitten  other  individuals  sick  with 
malaria.  To  avoid  the  criticism  that  these  experiments  were 
carried  on  in  Italy,  an  intensely  malarial  country,  where 
natural  infection  could  not  be  absolutely  excluded,  Patrick 
Manson  ^  had  a  number  of  infected  mosquitoes  sent  from 
Italy  to  England  in  1900,  and  caused  two  men,  Dr.  Thurburn 
Manson  and  Mr.  Warren,  who  had  never  been  in  a  malarial 
region,  to  be  bitten.  Both  men  developed  malaria  in  exactly 
eighteen  days.  In  the  same  year  Sambon  and  Low  lived  for 
three  months  in  the  most  malarial  section  of  the  Roman 
Campagna,  protecting  themselves  absolutely  against  the  bites 
of  mosquitoes,  but  taking  no  other  precautions.  They  did 
not  contract  malaria,  but  of  fifteen  or  sixteen  police  sent  from 
Rome,  who  spent  one  night  unprotected  in  the  same  place, 
every  one  developed  the  disease." 

Mosquito  Sole  Carrier  of  Malaria.  —  The  observations 
and  experiments  above  noted  prove  conclusively  that  malaria 
is  transmitted  by  the  bites  of  infected  anopheles  mosquitoes, 
but  do  not  indicate  whether  or  not  it  may  be  spread  in  other 

1  Patrick  Manson,  Brit.  M.  J.,  Lond.,  1900,  II,  949. 
»  Sambon  and  Low,  Brit.  M.  J.,  Lond.,  1900,  II,  1679. 


384       THE  SOURCES  AND  MODES  OF  INFECTION 

ways.  It  was  Manon's  theory  at  first  that  the  malarial  para- 
site is  transmitted  from  adult  to  larvse  by  means  of  the  water 
in  which  the  eggs  are  laid,  and  that  this  water  is  also  the 
means  of  infecting  human  beings.  He  suggested  that  germs 
might  be  inhaled  in  dust  from  dried-up  and  infected  pools. 
As  regards  transmission  by  water  the  experiments  of  Celli  ^ 
and  others  have  already  been  referred  to,  whicli  indicate  that 
such  a  mode  of  transference  is  highly  improbable,  and  there 
is  certainly  no  epidemiological  evidence  in  its  favor.  That 
the  Plasmodium  of  malaria  grows  outside  of  the  animal  body 
is  also  improbable,  for  it  has  never  been  possible  as  yet  to 
cultivate  it  in  any  way.^  It  has  never  been  found  in  the  water 
of  malarial  regions.'  Even  if  there  are  sporelike  forms  resist- 
ant to  drying,  there  is  strong  evidence  that  such  are  not  air- 
borne, for  mosquito  netting  would  in  no  way  interfere  with  the 
free  movement  of  particles  small  enough  to  be  wafted  by  the 
air;  but  abundant  evidence  has  shown  that  efficient  screening 
against  mosquitoes  affords  complete  protection  against  this 
disease,  even  in  the  most  intensely  malarial  regions.  More- 
over the  success  attending  methods  of  prevention  based  on 
the  mosquito  theory  point  indubitably  to  the  truth  of  the 
theory.  Experimental,  clinical  and  epidemiological  evidence 
combine  to  demonstrate  that  malaria  is  a  disease  transmitted 
solely  by  the  bites  of  infected  mosquitoes.  ^  There  are  several 
forms  of  malarial  fever,  such  as  tertian,  quartan,  aestivo-au- 
turanal,  apparently  caused  by  different  species  of  Plasmo- 
dium, but  there  is  no  need  here  of  considering  these  different 
forms  and  their  relation  one  to  another.  Suffice  it  to  say  that 
the  mosquito  appears  to  be  the  true  host  of  this  parasite,  and 
in  its  body  it  undergoes  sexual  reproduction.  From  eight  to 
ten  days  after  the  mosquito  is  infected,  its  entire  body,  in- 
cluding its  salivary  gland,  becomes  infested  with  the  so-called 
sporozoite  forms,  and  when  these  are  injected  into  human  be- 

'  Soo  ch.iptor  on  Infection  Ijy  Water. 

^  CraiK,  'Die  Malarial  Fevers,  New  York,  1909,  93. 

"  Craig,  idem,  S3. 


INFECTION  BY  INSECTS  385 

ings  they  continue  to  undergo  a  vegetative  or  asexual  prolifera- 
tion, the  successive  phases  of  which  give  rise  to  the  symptoms 
of  the  disease.  It  is  believed  that  no  vertebrate  other  than 
man  serves  as  the  host  of  the  Plasmodium,  and  until  recently 
it  was  thought  that  no  mosquitoes  except  those  belonging  to 
the  genus  Anopheles  could  transmit  the  disease;  but  recent 
observations  in  the  Philippines  '  indicate  that  a  mosquito 
breeding  in  salt  marshes,  Myzomyia  ludlowii,  may  become  the 
host  of  the  Plasmodium.  But  it  is  certain  that  almost  always 
it  is  some  species  of  Anopheles  which  is  the  carrier.  Not  all 
Anopheles,  however,  can  serve  as  the  host,  for  one  of  our 
common  species  in  the  northern  United  States,  A.  puncti- 
pemiis,  does  not.' 

Habits  of  Mosquitoes.- — Mosquitoes  develop  only  in  water. 
The  larval  and  pupal  stages  may  occupy  from  eight  days  to  a 
number  of  weeks,  or  the  larvae  may  even  live  all  winter 
under  the  ice  in  northern  regions,  or  retain  their  vitality  for 
some  time  in  the  dried  mud  of  the  tropics.  The  mature 
insects  usually  live  only  a  few  weeks,  but  in  northern  regions 
hibernate  during  cold  weather.  The  habits  of  life  of  the  dif- 
ferent species  of  Anopheles  vary  considerably,  and  should  be 
carefully  studied  when  measures  for  extermination  are  under- 
taken. Only  the  adult  female  bites,  so  she  alone  is  the  carrier 
of  the  disease.  Anopheles  usually  bite  at  night.  Gorgas^  states 
that  they  do  not  usually  fly  above  100  yards,  and  that  clearing 
and  draining  the  area  within  this  distance  of  houses  affords 
great  protection.  Nevertheless  it  sometimes  happens  that 
under  favorable  conditions  the  insects  may  be  carried  a  con- 
siderable distance  by  the  wind.  Craig*  states  that  they  may 
be  borne  even  two  and  one-half  miles. 

Must  be  Many  Mosquitoes.  —  Mosquitoes  are  not  infected 
with  the  malarial  parasite  unless  they  bite  infected  human 

1  Banks,  Philippine  J.  Sc.  [B.  Med.j,  1908,  III,  335. 

»  Hirschberg,  Johns  Hopkins  Hosp.  Bull.,  Bait.,  1904,  XV,  53. 

^  Gorgas,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1967. 

*  Craig,  The  Malarial  Fevers,  New  York,  1909,  69. 


386       THE  SOURCES   AND   MODES   OF   INFECTION 

beings.  The  number  of  infected  mosquitoes,  then,  varies  with 
the  number  of  infected  persons  to  whom  they  have  access. 
Craig  '  refers  to  the  findings  of  himself  and  others  as  varying 
from  35  per  cent  to  O.G  per  cent.  For  the  spread  of  malaria  it 
is  necessary  that  there  should  be  Anopheles  and  human  beings 
infected  with  the  parasites.  But  if  the  mosquitoes  are  not 
numerous  and  the  cases  of  infection  are  not  numerous,  the 
chances  of  a  mosquito  becoming  infected  and  then  biting 
another  victim  after  a  proper  interval  are  not  great,  so  that  it 
may  happen  that  there  may  be  mosquitoes  and  human  infec- 
tion without  extension  of  the  disease.  Thus  it  is  not  known 
that  cases  of  malaria  have  ever  developed  on  the  island  of 
Rhode  Island, but  I  ha  ve  found  a  few /I  nop/icZes  breeding  there, 
and  with  the  great  numbers  of  summer  visitors  from  all  over 
the  world,  and  many  soldiers,  and  sailors  of  the  navy,  it  is 
probable  that  the  malarial  parasite  is  frequently  present  on 
the  island.  These  epidemiological  facts  led  me  for  some  time 
to  suspect  that  the  supposed  mode  of  transmission  of  this 
disease  above  outlined  did  not  contain  the  whole  truth;  but 
the  directness  and  strength  of  the  experimental  proof,  and, 
above  all,  the  success  of  mosquito  control  in  checking  the 
disease  render  it  certain  that  practically  the  only  way  in 
which  malarial  disease  is  caused  is  by  the  bites  of  mosquitoes. 
There  are  numberless  interesting  details  connected  with  the 
life  history  and  habits  of  the  mosquito  which  are  of  great 
importance  but  which  cannot  be  considered  here.  The  way 
in  which  these  habits  explain  tlu^  peculiarities  in  the  develop- 
ment of  malaria  is  well  considered  by  Nuttall." 

Ways  of  Prevention.  —  There  are  several  ways  in  which 
the  spread  of  malarial  disease  may  })e  checked. 

First.  Quinia.  —  The  administration  of  the  various  salts  of 
quinia  prevents  the  development  of  the  malarial  parasite  in 
the  blood,  and  tiiis  drug  is  an  extremely  valuable  remedy  in 
the  prevention  and  cure  of  malaria.     Antitoxin  and  vaccines 

1  CraiR,  lof.  cit.,  74. 

»  Nuttall,  John.s  Hopkins  IIosp.  llcp,,  Bull.,  1S99,  VIII,  78, 


INFECTION  BY  INSECTS  387 

are  of  great  value  in  the  prevention  and  cure  of  certain  of  the 
infectious  diseases,  as  diphtheria,  typhoid  fever  and  cholera, 
but  they  are  of  value  chiefly  to  the  individual.  The  difficulties 
attendant  upon  their  administration  are  so  great  that  they 
cannot  be  used  except  in  rare  instances  to  protect  large  bodies 
of  people.  The  antitoxins,  too,  probably  do  not  prevent  the 
growth  of  the  germs  which  are  the  cause  of  the  disease,  so 
that  in  a  way  their  use,  as  for  instance  that  of  diphtheria 
antitoxin,  may  actually  in  some  instances  favor  the  spread  of 
the  disease,  by  preventing  the  development  of  symptoms 
when  the  bacilli  are  present,  thus  making  a  "carrier"  instead 
of  a  ''case,"  and  carriers  are  always  difficult  to  control.  It  is 
otherwise  with  quinia.  This  drug  actually  kills  the  Plas- 
modium or  drives  it  out  of  the  circulation  and  out  of  the 
way  of  the  mosquito,  and  so  not  only  protects  the  individual 
but  prevents  him  from  becoming  a  focus  of  infection.  Quinia 
is  not  only  universally  used  as  a  specific  curative  agent,  but  it 
is  also  employed  in  large  quantities  as  a  prophylactic,  and  its 
employment  in  this  manner  is  considered  a  valuable  means  of 
fighting  the  disease,  reducing  as  it  does  the  number  of  foci  of 
infection.  Indeed  Koch  and  some  others  claim  that  this  is 
the  only  way  in  which  malaria  can  be  eradicated,  as  mosquito 
destruction  is  in  many  places  impossible.  All  workers  in  this 
field  employ  quinia  for  this  purpose,  though  there  is  con- 
siderable discussion  as  to  its  mode  of  administration,  which 
varies  from  15  grains  every  eight  days,  as  used  by  Koch,  to 
3  grains  daily,  as  advised  by  Gorgas.  This  subject  is  fully 
discussed  by  Craig, ^  who  states  that  in  the  vast  majority  of 
instances  2j  grains  (0.15  grm.)  daily  is  sufficient  to  prevent 
malarial  infection.  It  is  difficult  to  estimate  the  value  of  a 
particular  prophylactic  measure,  for  one  measure  is  rarely 
used  alone,  but  there  is  little  doubt  of  the  great  efficiency  of 
quinia  in  the  fight  against  malaria.  Craig  states  that  at 
Camp  Stotsenburg,  in  the  Philippines,  measures  directed 
against  mosquitoes  had  little  result  until  supplemented  by 
»  Craig,  The  Malarial  Fevers,  New  York,  1909,  343. 


388       THE  SOURCES  AND  MODES  OF  INFECTION 

the  daily  administration  of  quinia.  Koch  and  his  followers 
also  report  excellent  results  from  the  use  of  quinia  alone. 
Celli,^  while  urging  every  method  directed  against  the  mos- 
quito, considers  that  in  Italy  experience  has  shown  that  the 
daily  administration  of  quinia  has  been  the  most  effective 
measure  in  reducing  the  number  of  deaths  from  malaria, 
which  have  fallen  steadily  from  13,861  in  1901  to  4871  in  1906, 
during  which  year  20,723  kilos  of  quinia  were  sold. 

Second.  Isolation  of  Persons.  —  The  attempt  may  be 
made  to  isolate  the  infected  persons  so  that  the  mosquitoes 
may  not  pass  from  them  to  the  healthy.  This  may  be  accom- 
plished in  various  ways.  In  many  tropical  regions  where 
the  native  population,  or  at  least  the  native  children,  are 
always  infected,  the  dwellings  of  the  natives  and  the  sus- 
ceptible Europeans  are  separated  a  sufficient  distance  to 
escape  the  ordinary  excursions  of  the  mosquitoes. 

Sometimes  the  patients,  if  few  in  number,  are  screened  from 
mosquitoes  in  their  own  homes  or  are  removed  to  screened 
hospitals.  This  is  very  commonly  done  with  the  imported 
cases  which  come  to  Havana,"  and  in  Panama  many  malarial 
patients  are  treated  in  the  screened  hospitals.  Others  are 
cared  for  in  their  own  well-vscreened  houses. 

To  assist  in  this  measure  it  is  desirable  to  kill  all  mosquitoes 
in  the  house  which  may  have  bitten  the  patient  before  the 
disease  was  recognized  or  reported  to  the  authorities.  Gor- 
gas  considers  sulphur  dioxid  the  best  for  this,  but  as  this 
cannot  be  used  in  an  occupied  room,  pyrethrum  may  be 
burned,  which  so  stupefies  the  insects  that  they  may  be  easily 
swept  up  from  the  floor.  Celli  has  given  much  study  to  this 
class  of  culicides  and  re(;ominonds  one  or  two  tablespoonfuls 
of  a  mixture  of  the  unexpaiided  flow(^rs  of  chrysanthemum 
and  valerian  root. 

Third.  Screening. —  Effort  should  be  made  in  all  malarious 
regions  to  protect  susceptil^k;  persons  from  the  bites  of  mos- 

»  Quoted  by  Craig,  The  Malarial  Fevers,  Now  York,  1909,  345. 
*  Guiteras,  J.  Am.  M.  Aaa.,  Chicago,  1909,  LIII,  1165. 


INFECTION  BY  INSECTS  389 

quitoes.  The  screening  of  the  whole  house  is  the  most  impor- 
tant step.  Copper  netting  is  the  cheapest  in  the  end,  and  it 
should,  according  to  Craig,  have  11  meshes  to  2  cm.  Gorgas 
says  that  it  is  necessary  that  houses  should  be  screened  by 
persons  experienced  in  mosquito  work,  or  openings  are  sure 
to  be  left.  The  experiments  of  Sambon  and  Low  proved  the 
efficacy  of  this  method  of  prophylaxis,  and  Craig  states  that 
the  screening  of  the  houses  of  railway  employees  on  certain 
Italian  lines  has  been  as  effectual  a  method  as  the  administra- 
tion of  quinia.  Screening  is  carried  on  most  extensively  in 
the  Canal  Zone.  Craig  says  that  where  screening  is  impos- 
sible the  use  of  mosquito  canopies  over  the  beds  at  night  is 
a  very  useful  measure,  and  head  nets  and  gloves  for  men 
obliged  to  be  out  at  night  are  of  much  value.  By  the  use  of 
these  methods  the  percentage  of  malaria  among  troops  in 
Sardinia  was  reduced  from  70  to  20,  and  in  Formosa  no  mala- 
ria developed  among  115  soldiers  protected  by  netting,  while 
of  717  not  so  protected  251  were  attacked. 

The  removal  of  trees,  vines  and  shrubs  from  the  vicinity 
of  dwellings  is  considered  by  Gorgas  an  important  measure, 
as  these  serve  as  hiding  places  for  the  insects  by  day.^ 

A  certain  amount  of  protection  may  be  secured  by  the 
application  to  the  skin  of  substances  annoying  to  the  mos- 
quito, or  of  ointment  which  mechanically  interferes  with 
biting.  Oil  of  citronella  or  eucalyptus,  and  petroleum  or 
cocoanut  oil  or  vaseline,  are  used,  but  such  applications 
are  not  by  most  writers  considered  of  much  value. 

Fourth.  Mosquito  Prevention.  —  Theoretically  the  most 
effectual  way  to  eradicate  malaria  is  to  prevent  the  growth  of 
mosquitoes.  While  their  complete  destruction  is  not  usually 
possible,  its  attempt  must  always  take  first  rank  in  preventive 
measures.  The  fact  that  mosquitoes  are  a  great  nuisance, 
as  well  as  carriers  of  disease,  makes  still  more  desirable  their 
extermination  wherever  possible.  Large  sums,  in  certain 
parts  of  the  United  States,  are  being  expended  in  fighting  the 
1  Gorgas,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1967. 


390       THE  SOURCES  AND  MODES  OF  INFECTION 

salt-marsh  mosquito,  which  is  harmless  so  far  as  carrying 
disease  is  concerned. 

Fifth.  Draining.  —  When  mosquitoes  breed  in  pools  and 
swamps,  as  they  so  often  do,  draining  and  filling  must  be 
done.  If  water  cannot  be  entirely  gotten  rid  of,  the  banks  of 
streams,  ponds  and  ditches  must  be  straightened  and  deepened, 
and  freed  from  vegetation,  to  remove  hiding  places  for  the 
larvae  and  permit  their  destruction.  Gorgas  insists  upon  the 
importance  of  having  this  work  done  by  men  especially  trained 
for  it,  and  supervised  by  experts.  Ordinary  contractors  and 
laborers  are  sure  to  overlook  breeding  places  and  to  neglect  im- 
portant details  of  the  work.  Many  species  of  Anopheles  breed 
in  cisterns  or  accidental  receptacles  of  water  near  houses. 
Hence  all  such  should  either  be  removed  or  carefully  screened. 

Sixth.  Oiling. —  The  growth  of  larvae  in  water  can  be  pi'e- 
vented  by  the  application  of  crude  petroleum  or  kerosene  to 
the  surface  at  the  rate  of  an  ounce  to  each  15  square  feet  of  sur- 
face. Various  poisonous  substances  may  be  added  to  the  water, 
as  hydrochloric  acid,  corrosive  sublimate,  formalin,  chloride 
of  lime  and  various  aniline  dyes.  Some  of  the  last  named 
are  strongly  recommended  by  Colli,  as  they  are  harmless  to  the 
higher  animals.  The  use  of  quicklime  causes  a  glaze  on  the 
surface  which  is  a  protection,  and  sulphate  of  copper  kills  the 
algffi  on  which  the  mosquitoes  live.  Most  fish  are  voracious 
feeders  on  the  larvae,  and  if  pools  and  streams  are  supplied 
with  fish,  and  kept  free  from  weeds,  mosquitoes  cannot  thrive. 
It  is  said  that  the  introduction  of  a  certain  small  fish  into 
the  streams  of  Burl^ados  caused  the  extermination  of  mos- 
quitoes.^ According  to  Craig,  the  application  of  cultures  of 
Aspergillus  nigcr  and  .1.  glaucus  destroys  the  larvae. 

Success  of  Measures.  —  There  is  probably  scarcely  a 
locality  in  which  the  application  of  a  single  prophylactic 
measure  will  be  found  offec^tual  in  "  stamping  out  "  malaria, 
and  sometimes  all  methods  combined  fail  to  bring  success. 
'Thus  at  Mian  Mir  in  India,  according  to  Craig,  the  most 
1  Ballou,  Nuturc,  Loud.,  1909,  LXXX,  16. 


INFECTION  BY  INSECTS  391 

careful  draining  and  oiling  were  followed  by  very  discourag- 
ing results.  On  the  other  hand,  preventive  measures  have  in 
many  localities  given  wonderfully  good  results.  The  success 
of  the  work  in  Italy,  as  reported  by  Celli,  has  already  been 
referred  to.  In  Havana  the  deaths  from  malaria  previous 
to  the  occupation  by  the  United  States  averaged  350  per 
annum,  rising  to  1907  in- 1898.  The  measures  carried  out  by 
Gorgas  to  destroy  the  yellow-fever  mosquitoes  also  practi- 
cally eliminated  the  Anopheles,  and  the  deaths  now  average 
only  about  40,  and  three-fourths  of  these  are,  according  to 
Kean,^  due  to  infection  contracted  elsewhere.  At  Ismailia " 
the  cases  were  reduced  from  2284  in  1900  to  37  in  1905, 
chiefly  by  destroying  the  breeding  places  of  mosquitoes.  At 
Klang  and  Port  Swettenham  in  the  Federated  Malay  States 
99  per  cent  of  the  mosquitoes  were  eliminated,  with  a  corre- 
sponding decrease  in  malaria.  Ross  also  refers  to  the  success- 
ful reduction  of  malaria  at  Port  Said,  Durban,  Hong  Kong, 
Khartoum,  and  in  Candia,  St.  Lucia,  Greece  and  Algeria.^ 

Success  in  Panama.  —  To  my  mind  the  most  wonderful 
success  of  all  has  been  attained  by  Gorgas  in  the  Panama 
Canal  Zone.  Here  was  a  stretch  of  territory  45  miles  long, 
intensely  malarious,  nowoccupied  by  a  force  of  44,000  persons, 
mostly  foreigners.  The  rainfall  is  heavy,  and  the  work  of 
canal  building  alters  in  every  direction  the  configuration  of 
the  land  and  the  natural  drainage.  Malaria  caused  enor- 
mous losses  during  the  French  occupation  and  was  second 
only  to  yellow  fever  in  interrupting  the  work.  Mosquitoes 
have  been  entirely  eliminated  from  Colon,  a  town  of  15,000 
inhabitants,  and  the  death  rate  from  malaria  among  employ- 
ees was  only  1.34  per  thousand  in  1908,  having  been  reduced 
from  5.57  in  1905.  Considering  the  tremendous  obstacles  to 
be  overcome,  this  success  is  certainly  astonishing.* 

'  Kean,  J.  Am.  M.  Ass.,  1909,  LIII,  1166.  " 

2  Ross,  Lancet,  Lond.,  1907,  II,  879. 

3  Ross,  Nature,  Lond.,  1909,  LXXX,  415. 

*  Gorgas,  J.  Am.  M.  Ass.,  Chicago   1909,  LII,  1967. 


392        THE  SOURCES  AND  MODES  OF  INFECTION 


Yellow  Fever. 

History  of  Discovery.  —  Nott  appears  to  have  been  the 
first  (1848)  to  attribute  to  mosquitoes  a  role  in  the  causation 
of  yellow  fever,  but  this  was  merely  a  suggestion  which  re- 
ceived little  attention.  According  to  Cruz/  Beauperthuy 
published  on  the  23d  of  May,  1854,  in  the  Official  Gazette  of 
Cumana,  Venezuela,  an  article  which  expounded  with  great 
clearness  a  mosquito  theory  of  this  disease.  But  to  Finlay 
of  Havana  is  due  the  credit  for  the  first  experimental  work,  a 
report  of  which  was  presented  to  the  Royal  Academy  of  Medi- 
cal, Physical  and  Natural  Sciences  in  Havana  in  1882.  Finlay 
continued  to  experiment  and  write  until  1900,  when  the 
American  Commission,  consisting  of  Reed,  Carroll,'  Agra- 
monte  and  Lazear,  undertook  their  investigations  at  Havana.^ 
Finlay  had  come  to  the  conclusion  that  Culex  fasciatusl  now 
Stegomyia  calopus,  was  the  species  of  mosquito  which  was 
likely  to  be  involved  in  the  transmission  of  the  disease.  After 
the  occupation  of  Cuba  by  the  United  States  in  1898,  the 
war  department  undertook  with  great  energy  the  extirpation 
of  yellow  fever  from  Havana.  At  that  time  the  disease  was 
believed  to  be  essentially  a  filth  disease,  and  the  energy  of 
the  government  was  directed  towards  making  Havana  clean, 
and  soon  its  "sanitary  condition"  vied  with  that  of  the  very 
best  cities  in  the  United  States.  At  the  same  time  thF'most 
stringent  measures  of  isolation,  as  isolation  was  at  that  time 
understood,  were  applied.  But  yellow  fever  refused  to  be 
stamped  out,  and  in  1900  caused  1244  cases  and  310  deaths, 
many  of  them  among  the  "  best  people  "  in  the  cleanest  parts 
of  the  city.^  It  was  becoming  evident  that  the  old  theories 
were  not  satisfactory,  and  the  war  department  appointed  the 

1  Cruz,  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Pub.  Health  Rep., 
Waiih.,  1909,  XXIV,  1741. 

*  Loc,  Am.  Pub.  Health  Ass.  Rep.,  1905,  XXX,  8. 

»  Series  4,  Yellow  Fever  Pub.,  San.  Dept.,  Havana,  1902,  10. 


INFECTION  BY  INSECTS  393 

commission  above  referred  to,  which  proceeded  to  Havana 
and  in  its  earliest  work  put  Finlay's  mosquito  theory  to  the 
test.  They  were  not  a  httle  influenced  to  this  step  by  the 
observations  of  Carter.^  He  had  determined,  from  a  study 
of  the  disease  in  isolated  farmhouses,  that  from  nine  to  six- 
teen days  usually  elapse,  after  the  introduction  of  the  disease, 
before  the  house  can  infect  second  cases.  It  was  thought 
that  this  interval  might  depend  upon  a  period  of  incubation 
in  the  mosquito.  Owing  to  the  hearty  cooperation  of  General 
Wood,  the  governor,  himself  a  medical  man,  every  facility 
was  accorded  the  commission,  and  inoculation  experiments 
were  made  on  volunteer  human  subjects,  among  whom  was 
Lazear,  a  member  of  the  commission.  Of  11  persons  bitten 
by  mosquitoes  which  had  some  days  before  been  allowed  to 
feed  on  a  yellow-fever  patient,  2  developed  the  disease,  one 
of  whom  was  Lazear,  who  died  as  the  result  of  the  inoculation.^ 
Carroll  too  was  bitten  and  developed  the  disease.  As  critics 
suggested  that  natural  infection  could  not  be  excluded,  the 
experiments  were  repeated  in  November  and  December, 
1900,  under  more  convincing  conditions,  and  6  of  7  persons 
bitten  developed  typical  yellow  fever,  and  the  transmission 
of  the  disease  in  this  manner  was  demonstrated  beyond  ques- 
tion.^ Later  Guiteras  *  succeeded  in  inoculating  8  more  per- 
sons, which  made  a  total  of  24  persons  infected  by  the  bites 
of  mosquitoes.  Of  these  3  died,  and  the  post-mortem  ex- 
amination demonstrated  the  lesions  of  yellow  fever.  The 
commission  had  by  the  direct  transfer  of  blood  shown  that 
the  infective  agent  exists  in  that  fluid,  even  when  filtered.* 
All  the  experimenters  demonstrated  that  the  mosquito  could 
not  transmit  the   disease  until  six  to  eighteen  days  after 

1  New  Orleans  M.  &  S.  J.,  1900,  LII,  617. 

2  Am.  Pub.  Health  Ass.  Rep.,  1900,  XXVI,  37;  Phila.  M.  J.,  1900, 
VI,  790. 

'  Series  3,  Yellow  Fever  Pub.,  San.  Dept.,  Havana,  1902. 

*  Series  6,  Yellow  Fever  Pub.,  San.  Dept.,  Havana,  1902,  26. 

'  Am.  Med.,  Phila.,  1902,  III,  301. 


394       THE  SOURCES  AND  MODES  OF  INFECTION 

biting  a  yellow-fever  patient,  thus  explaining  the  wonder- 
fully accurate  clinical  observations  of  Carter.  Although  it 
has  been  shown  that  filtered  blood  contains  the  infective 
principle,  thus  far  it  has  not  been  demonstrated  by  micro- 
scopical or  cultural  methods.  It  seems  in  the  highest  degree 
probable,  from  this  very  remarkable  work,  that  the  exciting 
agent  of  yellow  fever  closely  resembles  that  of  malaria,  in 
that  it  is  found  in  the  blood,  is  taken  up  by  a  particular 
species  of  mosquito,  develops  in  the  mosquito  during  a  period 
of  some  days,  and  is  then  transmitted  to  new  subjects  only 
by  the  subsequent  bites  of  the  insect. 

Transmission  by  Fomites  Disproved.  —  Belief  in  the  infec- 
tiousness of  the  vomitus  and  excreta  and  in  the  important 
part  played  by  fomites  in  the  extension  of  the  disease  was 
so  firmly  fixed  that  it  seemed  necessary  to  test  this  theory 
by  actual  experiment.  The  commission  for  this  purpose 
exposed  a  number  of  non-immune  persons  to  the  closest 
possible  contact,  during  a  period  of  two  weeks,  to  bedding, 
clothing  and  other  articles  all  grossly  contaminated  with 
supposedly  infective  material,  but  none  of  them  contracted 
the  disease.  Later  Guiteras,  while  carrying  on  his  mosquito  in- 
oculations, incidentally  exposed  many  non-immunes  to  fabrics 
that  had  been  in  close  touch  with  yellow-fever  cases,  but  with 
like  negative  results;  and  again  Gorgas,  at  Las  Animas  Hos- 
pital in  Havana,  put  the  fomites  theory  to  test  in  the  most 
thorough  manner  by  the  exposure  of  non-immunes  to  close 
and  continued  contact.' 

Even  before  these  demonstrations,  some  acute  observers, 
especially  Carter,^  had  concluded  from  epidemiological  studies 
that  fomites  played  little  part  in  the  dissemination  of  this 
disease.  Carter  showed  among  other  things  that  countless 
pieces  of  baggage,  many  of  them  certainly  from  infected 
houses  in  Cuba  and  Vera  Cruz,  had  passed  to  northern  porta 
without  causing  yellow  fever  in  a  single  instance. 

1  Series  3,  Yellow  Fever  Pub.,  San.  Dept.,  Havana,  1902,  22. 
»  Carter,  Med.  News,  N.  Y.,  1904,  LXXXV,  878. 


INFECTION  BY   INSECTS  395 

Transportation  of  Mosquitoes.  —  Theoretically  there  is  no 
reason  why  infected  mosquitoes  might  not  occasionally  be 
carried  in  baggage,  but  admission  of  baggage  without  dis- 
infection, without  any  known  instance  of  the  development  of 
yellow  fever,  shows  that  such  a  mode  of  transmission  must 
be  extremely  rare.  Even  the  carriage  of  infected  mosquitoes 
in  vessels  must  be  unusual,  though  instances  are  recorded  by 
Carter  ^  and  others.  Grubbs  "  found  Stegomyia  calopus  on 
three  of  sixty-five  vessels  entering  the  Gulf  Quarantine  Sta- 
tion. Souchon,^  at  New  Orleans,  found  that  2.5  per  cent  of 
the  mosquitoes  caught  on  incoming  steamers  from  Havana 
or  the  West  Indies  were  Stegomyia  calopus.  Probably  none 
of  these  were  infected. 

The  rapid  and  brilliant  demonstration  of  the  true  mode  of 
extension  of  yellow  fever  was  immediately  followed  by  an 
equally  rapid  and  brilliant  application  of  the  new  knowledge. 
Two  months  after  the  termination  of  the  commission's  ex- 
periments, Gorgas  was  as  energetically  applying  the  new 
methods  of  yellow-fever  control  in  Havana  as  he  had  pre- 
viously devoted  himself  to  cleansing  the  city,  and  within 
eight  months  the  Stegomyia  calopus  had  been  nearly  exter- 
minated, and  Havana  was  free  from  the  disease  for  the  first 
time  in  150  years. 

Habits  of  Yellow-fever  Mosquito.  —  Different  species  of 
mosquitoes  haye  different  habits  of  life,  and  Stegomyia  calopus 
is  much  more  of  a  domestic  mosquito  than  are  the  Anopheles. 
It  prefers  to  breed  in  clean  rain  water,  but  will  grow  in  any 
water  that  is  not  too  muddy.  It  may  even  be  found  in  cess- 
pools and  in  gutters,  but  its  favorite  home  is  the  rain-water 
cistern,  barrel,  jar  or  other  container  which  is  usually  pro- 
vided for  every  house.  It  seems  to  prefer  dark,  covered  recep- 
tacles. The  adult  mosquito  is  rather  feeble  and  rarely  flies  far. 

1  Carter,  Med.  Rec,  N.  Y.,  1902,  LXI,  441. 

^  Grubbs,  Yellow  Fever  Institute,  U.  S.  Pub.  Health  &  Mar.  Hosp. 
Serv.,  Bull.  No.  11. 

'  Souchon,  J.  Am.  M.  Ass.,  Chicago,  1903,  XL,  1647. 


396       THE  SOURCES  AND   MODES  OF   INFECTION 

Preventive  Measures.  —  The  defensive  measures  against 
yellow  fever  must  of  course  be  somewhat  like  those  directed 
against  malaria,  but  differ  in  some  important  particulars. 
The  most  important  of  these  is  that  there  is  no  drug  which 
will  prevent  and  cure  this  disease  as  quinia  does  malaria. 
Another  point  of  difference  is  that  yellow  fever  is  not  nearly 
so  widespread  a  disease  as  is  malaria,  and  that  it  is  an  acute 
disease  in  which  the  patient  remains  infectious  for  only  a 
short  time.  Among  the  measures  directed  against  yellow 
fever  are: 

First.  Quarantine.  —  While  inland  quarantine  has  never 
been  successfully  administered,  maritime  quarantine  for 
yellow  fever  is  certainly  of  value.  The  short  period  of 
incubation  of  the  disease,  the  absence  of  chronic  cases 
and  the  fact  that  it  prevails  in  endemic  form  in  only  a 
few  places  which  are  in  communication  with  the  rest  of 
the  world  chiefly  by  water,  render  it  possible  to  intercept 
at  the  port  of  debarkation  a  goodly  number  of  incom- 
ing cases.  Quarantine,  while  often  failing,  has  many  times 
proved  its  value  in  the  United  States;  and  in  Havana,  after 
the  disease  was  exterminated,  it  would  certainly  have  many 
times  been  introduced  from  Vera  Cruz  and  Colon,  and  indeed 
probably  from  New  Orleans,  if  the  careful  inspection  of 
incoming  passengers  had  not  been  maintained  by  the  depart- 
ment of  health.  The  efficiency  of  quarantine  is  greatly 
increased  if  an  agent  is  stationed  at  the  port  of  embarkation, 
as  is  done  at  many  ports  by  the  United  States  Public  Health 
Service. 

Second.  Screening  of  Houses  and  Cases.  —  Houses  and 
their  healthy  inmates  must  be  screened  to  protect  them  from 
infected  mosquitoes,  and  cases  must  be  screened  to  prevent 
mosquitoes  from  becoming  infected.  Extraordinary  effort 
must  be  made  to  get  control  of  every  case.  The  harsh 
treatment  formerly  accorded  these  cases,  the  injury  to 
property  caused  by  disinfection  and  the  loss  to  business 
by  the  old  methods  of  quarantine  put  a  premium  on  con- 


INFECTION  BY  INSECTS  397 

cealment;  but  there  is  much  less  tendency  to  hide  cases  now 
than  formerly.  When  reported,  the  case  is  protected  from 
mosquitoes  either  by  efficient  screening  or,  as  is  now  usually 
-done  in  Havana  and  the  Canal  Zone,  by  removing  the  patient 
to  a  well-screened  hospital. 

Third.  Destruction  of  Mosquitoes.  —  Infected  mosquitoes 
in  the  house  occupied  by  the  patient  and  in  neighboring 
houses  must  be  destroyed.  Sulphur  dioxid  is  the  best  culi- 
cide  for  this  purpose,  but  pjTethrum  powder  may  be  burned 
while  the  room  is  occupied  and  the  stupefied  mosquitoes 
swept  up,  as  in  malaria. 

Fourth.  Prevention  of  their  Growth.  —  The  most  impor- 
tant means  of  preventing  yellow  fever  is  to  reduce  the  number 
of  stegomjaa  mosquitoes  to  a  minimum  by  destroying  their 
breeding  places  in  the  same  manner  in  which  the  breeding 
places  of  malarial  mosquitoes  are  destroyed,  by  draining,  fill- 
ing, ditching  and  the  use  of  petroleum  and  culicides  in  the 
water.  As  the  stegomyia  so  often  breeds  in  domestic  recep- 
tacles which  in  the  absence  of  a  municipal  water  supplj^  and 
sewers  cannot  be  dispensed  with,  the  efficient  screening  of 
these  receptacles  is  an  important  part  of  sanitary  work  in 
the  American  tropics,  and  constant  inspection  is  needed  to 
see  that  the  screening  is  maintained. 

Success  of  Measures.  —  The  phenomenal  success  of  these 
measures  in  Havana  has  already  been  referred  to,  but  the 
eradication  of  the  disease  in  the  Canal  Zone  is  a  still  more 
remarkable  achievement.  Havana  is  a  compactly  built,  well- 
drained  city,  and  was  under  military  rule.  The  Canal  Zone 
is  about  forty-five  miles  long,  with  swamps  and  streams,  many 
straggling  villages  and  camps,  a  heavy  rainfall,  continuous  high 
temperature,  a  constantly  changing  non-immune  population, 
stupendous  engineering  works  altering  the  configuration  of 
the  land,  and  a  persistent  yellow-fever  infection  for  centuries. 
This  disease  had  been  the  chief  obstacle  in  the  construction 
of  the  Panama  railroad,  and  it  was  the  chief  obstacle  to  the 
French  in  their  canal  work.     Their  loss  bv  death  from  this 


398       THE  SOURCES  AND  MODES  OF  INFECTION 

disease  amounted  probably  to  from  12  to  15  per  cent  per 
annum.'  Sanitary  work  began  on  the  isthmus  in  February, 
1905,  at  which  time  yellow-fever  cases  were  being  constantly 
reported.  The  cases  soon  began  to  decrease,  and  within  a 
year  the  disease  was  practically  exterminated.^  In  Rio  Ja- 
neiro the  campaign  against  yellow  fever  began  in  April,  1903. 
The  undertaking  was  expensive,  as  it  always  must  be  if  it  is 
to  be  successful.  It  required  the  expenditure  of  $1,650,000  a 
year  and  the  employment  of  thirteen  hundred  men.  Deaths 
from  yellow  fever,  which  had  averaged  twelve  hundred  a 
year  for  nearly  forty  years,  decreased  rapidly,  as  is  shown 
by  the  following: 

Year.  Deaths. 

1903 584 

1904 48 

1905 289 

1906 42 

1907 39 

1908 4 

1909 0 

In  Vera  Cruz,  which  was  another  stronghold  of  yellow 
fever,  the  disease  has  been  almost  eradicated  by  the  employ- 
ment of  anti-mosquito  measures.^ 

Filariasis. 

First  Parasite  Studied  in  Insects.  —  While  the  infection  of 
the  blood  of  man  with  Filaria  bancrofti  is  in  most  cases  not 
accompanied  by  noticeable  symptoms,  it  is  of  interest  in  this 
connection  as  being  the  first  infection  in  which  the  parasite 
was  proved  to  be  taken  up  into  and  undergo  metamorphosis 
in  the  body  of  an  insect.     This  tiny  worm  is  found  swimming 

'  Gorgas,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  597. 
2  Cruz,  Pul).  Health  Rop.,  U.  S.  Pub.  Health  &  Mar.  Hosp.  Scrv., 
Wash.,  1909,  1742. 

"  Liceaga,  Am.  Tub.  Health  Aaa.  Rep.,  1905,  XXXI,  284. 


INFECTION   BY   INSECTS  399 

in  vast  numbers  in  the  blood  of  those  who  are  infected,  but 
is  found  only  at  night.  During  the  day  it  disappears  from 
the  peripheral  circulation  and  is  found  only  in  the  heart  and 
lungs.  When  these  larval  forms  are  sucked  up  by  the  mos- 
quito they  increase  rapidly  in  size  and  become  more  highly 
organized,  and  working  their  way  to  the  proboscis  of  the 
insect,  infect  the  next  person  bitten.  The  worms,  now  pre- 
senting sexual  forms,  reach  the  lymph  ducts,  where  the  eggs 
are  laid  and  whence  the  young  larvae  reach  the  blood 
current.  It  is  now  generally  beheved  that  injury  to  the 
worms  in  the  lymph  vessels  causes  obstruction  of  the  latter 
and  the  development  of  tropical  elephantiasis.  Culex  fatigans 
is  probably  the  insect  chiefly  concerned  in  the  spread  of  the 
infection.  The  disease  has  not  been  actually  transmitted  to 
man  by  the  bites  of  infected  mosquitoes,  but  the  develop- 
ment of  the  worm  in  the  mosquito  was  observed  by  Manson 
in  1878^  and  by  Lewis  in  1879.^  A  similar  infection  in  dogs 
has  been  actually  transmitted  by  means  of  mosquitoes.^ 

Sleeping  Sickness. 

Discovery  of  Trjrpanosome.  —  The  trypanosome  (T.  gam- 
biensis),  which  is  the  cause  of  sleeping  sickness,  was  found 
in  the  blood  of  patients  by  Button  and  Todd  in  1901.  This 
disease  is  very  widely  distributed  in  Africa,  and  it  is  esti- 
mated to  have  caused  over  100,000  deaths  in  Uganda  during 
the  six  years  from  1901-1907.  This  trypanosome  is  patho- 
genic for  many  of  the  lower  animals,  and  in  monkeys  causes 
symptoms  resembling  those  produced  in  man.  Bruce  and 
Nabarro^  showed  that  the  disease  may  be  transmitted  by 
insects,  for  in  1903  they  succeeded  in  inoculating  a  monkey 
by  allowing  it  to  be  bitten  by  tsetse  flies  {Glossina  palpalis) 

»  Manson,  Med.  Times  &  Gaz.,  Lond.,  1878,  II,  731. 
2  Lewis,  Quart.  J.  Micr.  Sc,  Lond.,  1879,  XIX,  245. 
'  Braun,  The  Animal  Parasites  of  Man,  3d  ed.,  New  York,  1908,  285. 
*  Bruce  and  Nabarro,  Rep.  of  Sleeping  Sickness  Commission,  Roy. 
Soc,  1903,  No.  1. 


400       THE  SOURCES  AND  MODES  OF  INFECTION 

which  had  twenty-four  to  forty-eight  hours  previously  bitten 
negroes  suffering  with  the  disease.  While  this  much  has 
been  established  with  certainty,  there  are  important  points  in 
the  causation  of  the  disease  which  are  still  under  discussion. 

While  Glossina  -palpalis  is  known  to  transmit  sleeping  sick- 
ness, and  the  distribution  of  this  fly  in  a  large  degree  corre- 
sponds with  the  distribution  of  the  disease,  it  is  not  certain 
whether  it  may  not  be  carried  by  other  species  of  tsetse  flies, 
and  perhaps  by  domestic  insects  and  by  mosquitoes,^  and 
Koch  ^  thinks  it  possible  that  it  may  be  transmitted  by  the 
sexual  act.  Comparatively  little  is  known  about  the  breeding 
habits  of  the  fly. 

Does  it  infect  Lower  Animals?  —  There  has  also  been  much 
discussion  as  to  whether  the  specific  trypanosome  of  this 
disease  naturally  infects  the  lower  animals.  If  they  are  gener- 
ally affected,  they  become  a  vast  reservoir  from  which  the 
trypanosomes  may  be  transferred  to  human  beings  by  the 
fly,  and  the  difficulties  in  the  way  of  controlling  the  disease 
become  enormous.  Even  the  crocodile  has  been  suggested 
by  Koch  as  an  important  "reservoir."  But  Hodges^  says 
that  actual  observation  shows  that  no  animal  except  the 
native  dog,  and  that  in  only  a  few  instances,  has  been  found 
naturally  infected.  A  cause  of  the  uncertainty  is  a  wide- 
spread distribution  of  several  kinds  of  trypanosomes  not  easily 
distinguished  from  T.  gambiensis. 

Is  it  carried  Mechanically?  —  Another  question  of  impor- 
tance, especially  from  a  scientific  standpoint,  is  whether  the 
trypanosome  passes  through  a  cycle  of  development  in  the 
fly.  It  was  at  first  supposed  that  this  was  the  case,  but  later 
observations,  especially  those  of  Minchin,^  seemed  to  indicate 
that  this  was  not  so.     According  to  his  observations  flies  are 

1  Bull.  Son.  path,  oxot.,  Par.,  1908,  I. 

2  Koch,  D(Hit.srho  nicfl.  Wrhnschr.,  1907,  XXXIII,  1889. 

'  Citod  in  Hupl.  to  Third  Hep.,  Wcllconu'  liosoarch  Lab.,  Khartoum, 
1908,  III,  172. 

*  Minchin,  Quart.  J.  Micr.  Sc,  Lend.,  1908,  n.  s.,  LII,  159. 


INFECTION  BY   INSECTS 


401 


infective  at  once  after  biting  a  subject,  and  the  power  to 
infect  does  not  last  over  fortj^-eight  liours.  More  recently, 
however,  Bruce  ^  has  shown  that  the  parasites  do  undergo 
developmental  changes  in  the  fly,  and  that  flies  do  not  infect 
until  from  14  to  20  days  have  elapsed  after  feeding  on  a  case. 
Kleine  ^  also  has  demonstrated  the  same  for  other  forms  of 
trypanosomes.  It  is  possible  that  the  trypanosomes  may  be 
occasionally  carried  mechanically  on  the  proboscis  of  the 
tsetse  fly,  in  which  case  infection  will  take  place  at  once, 
and  also  that  the  parasites  pass  through  certain  metamor- 
phoses in  the  fly,  thus  permitting  the  flies  to  remain  infective 
for  some  time. 

Prevention  of  Sleeping  Sickness.  —  The  measures  sug- 
gested for  limiting  sleeping  sickness  are: 

First.  Quarantine,  or  the  prevention  of  the  entrance  of 
infected  human  beings  into  regions  occupied  by  the  fly. 
While  this  may  be  of  value  at  times,  it  scarcely  seems  possible 
to  an  observer  at  this  distance  that  it  can  be  often  employed 
effectually  in  Africa. 

Second.  The  sick  may  be  segregated  and  kept  out  of 
reach  of  the  flies  until  the  trypanosomes  have  disappeared 
from  the  blood. 

Third.  The  removal  of  the  entire  population  from  the 
area  occupied  by  the  fly.  The  tsetse  flies  are  found  only  from 
thirty  to  one  hundred  yards  from  water,  so  that  if  all  settle- 
ments are  removed  this  distance  from  rivers  and  lakes  much 
will  be  done  to  prevent  the  spread  of  the  disease. 

Fourth-.  As  trees  and  shrubs  afford  a  hiding  place  for  the 
flies,  the  thorough  clearing  of  the  land  around  villages  and 
near  landing  places  and  shore  market  places  has  been  found 
useful,  just  as  similar  clearing  has  been  found  to  be  an  impor- 
tant means  of  controlling  malaria  in  the  Canal  Zone  at 
Panama. 

1  Bruce,  Bull,  of  Sleeping  Sickness  Bu.,  1909,  Nos.  6  &  7. 

2  Kleine,  Deutsche  med.  Wchnschr.,  1909,  XXXV,  924. 


402       THE  SOURCES  AND  MODES  OF  INFECTION 

Fifth.  The  administration  of  atoxyl  (anilin  meta-arse- 
nate)  is  believed  by  many  to  shorten  the  Hfe  of  the  parasite 
in  the  body,  and  if  so,  it  becomes  a  valuable  prophylactic 
measure,  similar  to  the  use  of  quinia  in  malarial  affections. 

•     Kala-azar. 

Protozoan  Discovered  by  Leishman,  —  Kala-azar,  or  dum- 
dum fever,  occurs  in  various  tropical  countries,  particularly 
in  India.  It  runs  a  chronic  course  and  is  characterized  by 
marked  enlargement  of  the  spleen.  In  1900  Leishman  dis- 
covered in  splenic  pulp,  from  a  case  of  the  disease,  certain 
bodies  the  importance  of  which  he  did  not  appreciate,  but 
later,  in  1903,  he  concluded  that  they  might  be  protozoa. 
The  discovery  was  confirmed  the  same  year  by  Donovan. 
These  bodies  are  now  recognized  as  protozoa,  and  are  known 
as  Leishmania  donovani,  and  are  probably  the  cause  of  the 
disease.  Similar  bodies  were  found  by  Wright  of  Boston  in 
oriental  sore,  and  by  Nicolle  and  Cassuto  in  an  infantile 
splenic  disease  in  Tunis.  Rogers,  Patton  and  others  have 
succeeded  in  growing  the  parasite  in  culture  medium  outside 
of  the  body,  and  both  have  also  obtained  evidence  to  show 
that  the  disease  may  be  transmitted  by  the  bedbug.  Both 
Patton  and  Rogers  have  shown  that  a  well-defined  cycle  of 
development  takes  place  in  the  body  of  that  insect,  which 
renders  it  very  probable  that  it  is  the  intermediate  host. 
Patton  says,  "There  is  no  shadow  of  doubt  that  the  bed- 
bug transmits  the  disease,"  but  this  has  as  yet  not  been 
definitely  proved.^  Further  studies  by  Nicolle  and  others 
have  shown  that  the  dog  can  be  inoculated  with  the  type  of 
the  disease  occurring  in  Tunis,  and  furthermore  that  the 
disease  occurs  spontaneously  in  dogs  whi(^h  are  possibly  the 
source  of  the  human  disease.  In  Tunis  only  children  have 
so  far  been  observed  to  be  infected.  The  parasite  at  first 
was  thought  to  Ix'  somewhat  different  from  L.  infantum 

•  Siipplcmciils  to  Thini  and  I'\)urlJi  Heps.,  Wellcome  Research  Lab., 
Khartoum,  1908,  95;  1911,  150. 


INFECTION  BY  INSECTS  403 

but  the  two  forms  are  now  generally  believed  to  be  identical. 
Basile  thinks  the  flea  is  the  carrier,  while  Donovan  suspects 
some  species  of  Connorrhinus.  The  disease  has  recently 
been  observed  in  Italy,  Sicily,  Malta  and  Portugal.^ 

Pellagra.  —  Although  until  recently  the  majority  of 
writers  have  been  inclined  to  attribute  this  disease  to  the 
consumption  of  spoiled  maize,  Sambon  as  early  as  1905 
seems  to  have  suspected  that  it  might  be  a  true  contagious 
disease  transmitted  by  insects.  Sambon  considers  that  the 
topographical  distribution  of  the  disease  in  Italy  corresponds 
closely  with  the  distribution  of  a  small  biting  fly,  Simulium 
reptans.  Other  observers,  as  Alessandrini  and  Lavinder,^ 
agree  that  it  is  a  rural  disease  and  even  in  the  country  has 
a  "  patchy  "  distribution  as  has  malaria.  Sambon  and 
others  have  noted  its  prevalence  along  watercourses  and  its 
occurrence  is  confined  to  spring  and  autumn.  Sambon 
thinks  that  Simulium  is  the  carrier  because  it  has  the  same 
geographical  and  seasonal  distribution  as  pellagra  and  be- 
cause it  breeds  in  watercourses  along  which  pellagra  is 
found.  The  insect  does  not  enter  houses,  which,  according 
to  Sambon,  explains  the  limitation  of  the  disease  to  out-of- 
door  workers.  It  is  the  only  insect  which  has  the  same 
distribution  as  pellagra. 

Recently  in  South  Carolina^  the  relation  of  pellagra  to 
the  Simulium  vittatum  has  been  noted.  A  similar  relation 
has  been  reported  in  Kansas  by  Hunter.^ 

Opilacao  or  Canguary.  —  These  names  are  in  certain 
parts  of  Brazil  applied  to  hook-worm  disease,  but  in  the 
region  where  it  was  studied  by  Chagas  they  are  names  of  a 
quite  fatal  disease  of  children  characterized  by  dropsy, 
glandular    swellings    and    various    nervous    disturbances, 

1  Pub.  Health  Rep.,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  1911, 

XXVI,  1459. 

2  Pub.  Health  Rep.,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  1912, 

XXVII,  255. 

3  Hunter,  J.  Am.  M.  Ass.,  Chicago,  1912,  LVIII,  547.- 


404       THE  SOURCES  AND  MODES  OF  INFECTION 

especially  convulsions.  Chagas  found  the  disease  to  be 
characterized  by  the  presence  of  a  species  of  trypanosome 
named,  by  him,  Schizotrypanum  cruzi.  This  trypanosome 
is  also  found  in  various  animals  from  which  it  is  probably 
transmitted  to  man  by  a  large  biting  bug,  Connorrhinus 
megistus.  The  bugs  only  become  infective  on  the  eighth  to 
tenth  day  after  feeding.' 

Pappataci  Fever.  —  This  fever,  which  much  resembles 
dengue,  occurs  along  the  eastern  coast  of  the  Adriatic,  in 
Malta  and  Crete  and  probably  in  India.  Doerr  in  1908 
definitely  proved  that  it  is  transmitted  by  a  species  of 
"  sand  fly,"  Phlebotamus  papatassi.  The  cause  of  the  dis- 
ease is  probably  ultra-microscopic,  as  it  is  contained  in  the 
filtered  blood.  The  virus  is  transmitted  by  the  female  fly 
to  its  offspring  which  become  capable  of  causing  infection 
after  reaching  maturity.  The  habits  of  the  fly  have  been 
studied  and  plans  devised  for  its  control.^ 

Oriental  Sore.  —  This  is  also  variously  called  "  Bagdad 
boil,"  "  Biskra  boil,"  "  Aleppo  button  "  and  "  Bouton 
d'Orient."  It  is  also  found  in  Panama  and  in  Brazil,  as  well 
as  in  Asia  and  Africa.  The  parasite,  Leishmania  tropica, 
has  been  successfully  cultivated.  Inoculated  into  monkeys 
local  lesion  may  result,  but  these  animals  seem  not  to  be 
very  susceptible.  Although  the  parasites  are  not  found  in 
the  blood  it  has  been  thought  that  certain  biting  insects 
may  transmit  the  disease  after  becoming  infected  by  feed- 
ing on  the  sores.  Anopheles  mosquitoes  and  the  itch 
insect  have  been  suggested.  Wenyon^  has  made  careful 
studies  of  this  disease  in  Bagdad  and  has  succeeded  in 
getting  a  growth  of  the  parasites  in  bedbugs  and  mosquitoes 
but  not  in  ticks.     As  only  the  exposed  parts  of  the  body  are 

*  Second  Review  of  Recent  Progress  in  Tropical  Medicine,  Khar- 
toum, 1911,  371. 

2  Second  Review  of  Recent  Advances  in  Tropical  Medicine,  Khar- 
toum, 1911,  248. 

»  Wenyon,  Parasitology,  1911,  IV,  273. 


INFECTION  BY  INSECTS  405 

infected  he  thinks  it  improbable  that  bedbugs  transmit  the 
disease  but  suggests  a  sand  fly,  a  species  of  Phlebotamus,  or 
Stegomyia  fasciatus.  Wenyon  also  thinks  that  the  virus 
may  sometimes  be  carried  mechanically  by  flies. 

Typhus  Fever.  —  According  to  Wilder/  Mexican  physi- 
cians have  long  looked  upon  insects  as  carriers  of  "  tarba- 
dillo"  or  Mexican  typhus.  Recently  Sambon  suggested  the 
louse  as  perhaps  the  transmitter  of  this  disease,  and  in  1906 
Hay^  noted  many  epidemiological  facts  tending  to  impli- 
cate the  flea.  The  first  experimental  work  was  done  by 
Nicolle  and  his  associates  in  Tunis,  who  succeeded  in  trans- 
mitting the  typhus  fever  of  that  region  from  man  to  an  ape. 
Ricketts  and  Wilder^  and  Anderson  and  Goldberger,^  work- 
ing with  the  Mexican  type  of  the  disease  independently  of 
Nicolle,  demonstrated  conclusively  that  the  body  louse, 
Pedicuhis  vestinienti,  can,  under  experimental  conditions, 
easily  transmit  the  disease  from  inan  to  monkey  and  from 
monkey  to  monkey.  They  also  showed  that  the  virus  is 
contained  in  the  blood  and  is  filterable  and  that  one  attack 
protects  against  another.  Three  of  the  investigators  con- 
tracted typhus  fever  while  engaged  in  this  work  and  Ricketts 
died.  One  of  the  others,  Dr.  Goldberger,  writes  me  that 
while  experimenting  on  typhus  fever  he  was  bitten  by  a 
presumably  infected  louse.  Five  days  later  the  symptoms 
of  typhus  fever  developed. 

Some  experimental  evidence  was  secured  showing  that  in 
lice  the  infection  is  transmitted  to  offspring.  Some  work 
was  done  with  bedbugs  and  fleas  but  no  evidence  was  ob- 
tained except  of  a  negative  character.  Wilder  presents 
considerable  epidemiological  evidence  to  show  that  bed- 
bugs and  fleas  are  not  likely  to  be  the  carriers  of  this  disease. 

1  Wilder,  J.  Infect.  Dis.,  Chicago,  1911,  IX,  9. 

2  Pub.  Health,  Lond.,  1906-7,  XIX,  772. 

3  Ricketts  and  Wilder,  J.  Am.  M.  Ass.,  Chicago,  1911,  LIV,  1304. 
*  Anderson  and  Goldberger,  U.  S.  Pub.  Health  and  Mar.  Hosp. 

Serv.,  Pub.  Health  Rep.,  1910,  XXV,  177. 


406       THE  SOURCES  AND  MODES  OF  INFECTION 

Epidemiological  Evidence.  —  Typhus  fever  was  formerly 
considered  one  of  the  most  contagious  diseases,  and  at  the 
same  time  a  typical  filth  disease.  It  was  especially  rife  in 
camps  and  prisons  and  on  shipboard.  Physicians  and 
nurses  were  frequently  attacked.  An  impressive  record  of 
its  contagiousness  is  a  tablet  in  Bellevue  Hospital,  where  I 
served  as  an  interne,  on  which  are  inscribed  the  names  of 
the  medical  men  in  the  hospital  who  had  died  from  it.  In 
1864  of  21  members  of  the  staff  14  contracted  the  disease. 
Of  late  the  contagiousness  has  apparently  diminished.  It 
is  now  a  rare  disease  in  western  Europe  and  North  America 
(except  in  certain  parts  of  Mexico).  Outbreaks  are  usually 
easily  controlled  and  hospital  infection  is  comparatively 
rare.  Thus  600  cases  were  treated  in  the  City  Hospital, 
Liverpool,  without  a  single  case  of  hospital  infection.^ 
Wilder  says  that  in  the  American  Hospital  in  Mexico  144 
cases  were  treated  without  transfer  of  the  disease.  Hay  in 
Aberdeen,  while  noting  instances  of  infection  in  the  hospital 
during  the  outbreak  of  typhus  in  1906,  says  that  they  were 
very  few,  as  compared  with  former  times,  and  confined  to 
those  who  were  brought  in  contact  with  the  patients  before 
or  at  entrance  into  the  hospital.  Those  who  handled  the 
patients  after  they  were  cleansed  escaped.  In  the  typhus 
outbreak  in  New  York  in  1864,  as  stated  above,  14  of  21 
members  of  the  hospital  staff  contracted  the  disease,  while 
from  1881  to  1893,  during  which  time  there  were  1897  cases, 
most  of  which  went  to  the  hospital,  only  one  hospital 
physician  was  attacked,  namely  in  1884. 

New  Theory  Explains  the  Facts.  —  The  writer  has  always 
considered  the  decrease  in  typhus  fever  extremely  puz- 
zling. The  old-time  hygienists  were  in  the  habit  of  attrib- 
uting it  to  improvements  in  "  sanitation,"  meaning  thereby 
better  water  supply  and  drainage,  improved  scavenging  and 
better  housing,  but  no  one  explained  why  all  this  had  such 
a  mark(>d  eff(H't  upon  typhus  and  so  little  upon  smallpox, 
1  Roljiiuson  and  Potts,  Brit.  M.  J.,  1905,  I,  1137. 


INFECTION  BY  INSECTS  407 

scarlet  fever  and  diphtheria.  Again,  if  typhus  is  contagious 
by  the  same  means  as  are  the  diseases  just  named,  why 
should  isolation  "  stamp  out  "  typhus  and  do  nothing  of 
the  kind  for  scarlet  fever  and  diphtheria?  Much  light  is 
thrown  on  the  problem  if,  as  now  seems  probable,  the  louse, 
or  some  similar  insect,  is  the  chief  factor  in  the  transmission 
of  the  disease.  There  is  little  doubt  that  there  has  been  a 
vast  improvement  in  the  attitude  of  the  public  as  regards 
these  parasites,  and  the  poverty  and  squalor  which  favor 
their  presence  has  vastly  decreased  in  the  most  progressive 
nations  where  the  disease  no  longer  prevails.  In  prisons, 
hospitals  and  similar  institutions  lice  and  bedbugs  formerly 
abounded,  but  in  all  the  better  class  of  institutions  a  con- 
stant warfare  is  now  waged  against  them.  Thus  a  descrip- 
tion of  Bellevue  Hospital  in  1837,  where  typhus  fever  was 
then  prevailing,  reads  "  The  patients  were  lying  in  their 
filthy  blankets,  destitute  of  sheets  and  pillow  cases  and  in 
some  chronic  cases  they  had  not  had  a  change  in  three 
months."  Even  when  I  was  interne  in  1879  the  rooms  of 
the  staff  were  infested  with  bedbugs,  pediculosis  was  quite 
common  and  the  lodging  house  in  the  basement  was  out- 
rageously filthy  and  full  of  vermin  of  all  kinds.  The  con- 
trast furnished  by  most  modern  hospitals  is  marvelous. 
If  typhus  fever  is  spread  by  lice  no  wonder  that  it  has 
almost  vanished  from  our  institutions. 

Seasonal  Distribution.  —  Wilder  calls  attention  to  a 
number  of  points  in  which  this  mode  of  extension  fits  in 
with  the  epidemiology  of  the  disease.  Thus  typhus  is  a 
disease  of  temperate  climates,  and  lice  are  not  as  numerous 
in  the  tropics  as  in  cooler  regions,  and  on  account  of  light 
and  loose  clothing  their  parasitism  is  not  as  close.  In  addi- 
tion he  found  some  evidence  that  warm  weather  shortened 
the  persistence  of  the  virus  in  the  louse,  also  that  the 
seasonal  distribution  of  typhus  in  Mexico  corresponds  to 
the  seasonal  distribution  of  lice.  In  this  connection  it  may 
be  noted  that  Hamer-  found  in  London  that  the  maximum 


408       THE  SOURCES  AND  MODES  OF  INFECTION 

seasonal  prevalence  of  lice  is  in  January  and  the  minimum 
in  April,  May  and  June.^  The  seasonal  distribution  of 
typhus  in  London  is  not  so  marked  as  for  most  infectious 
diseases,  but  of  18,286  cases  admitted  to  the  London  Fever 
Hospital  the  maximum  number  was  in  January  and  30  per 
cent  were  admitted  during  the  first  three  months  of  the 
year.2 

The  marked  predilection  of  typhus  for  poverty  and  filth 
is  well  explained  on  this  hypothesis.  The  only  place  in 
America  where  typhus  prevails  is  on  the  Mexican  plateau 
where  Wilder  says  the  masses  are  grossly  lice  infested. 
Even  in  the  better  quarters  of  the  City  of  Mexico,  the  lousy 
lower  classes,  as  servants  and  otherwise,  are  brought  in 
such  frequent  contact  with  more  cleanly  people  that  pedi- 
culi  and  typhus  are  not  rarely  found  among  the  latter. 
Hay  called  attention  to  a  number  of  facts  which  he  thought 
tended  to  implicate  the  flea.  He  found  that  in  clean  houses 
and  among  clean  people  the  disease  did  not  spread.  The 
only  hospital  employees  who  contracted  the  disease  were 
in  contact  with  patients  before  the  latter  had  been  cleaned. 
Several  were  then  attacked.  No  cases  developed  in  the 
wards  after  the  patients  had  been  cleansed.  He  was  per- 
haps led  to  suspect  fleas  because  of  the  flea  bites  noted  on 
the  patients,  but  fleas  and  lice  are  often  together,  and 
Wilder  and  Anderson  and  Goldberger,  judging  from  epi- 
demiological as  well  as  from  experimental  data,  believe  that 
the  louse  is  the  chief  factor  in  the  spread  of  the  disease. 

Such  recent  writers  as  McVaiP  and  Ker^  consider  typhus 
above  all  things  an  air-borne  disease,  though  they  also  state, 
as  do  others,  that  its  "  striking  distance  "  is  remarkably 
short.     The  short  striking  distance;  is  easily  explained   if 

'  Hamer,  Rop.  Med.  Off.  Ilealtli  to  London  Co.  Council,  1909, 
Append.  IV,  8. 

2  lilytli,  A  Manual  of  Public  Health,  Loud.,  1S90,  401. 

'   McVail,  The  Prevention  of  Infei^tious  Diseases,  Loml.,  1907,  46. 

<  Ker,  Infectious  Diseases,  Lond.,  1909,  202. 


INFECTION  BY  INSECTS  409 

lice  are  the  carriers.  So  also  it  is  easy  to  understand  how 
clothing  may  at  times  transmit  infection,  as  is  said  to  be 
the  fact.  Thus  Wilson  ^  reports  an  instance  in  Belfast 
-where  the  disease  was  probably  carried  in  this  manner  in 
a  shawl,  yet  according  to  the  observations  of  Doty  (page 
216)  such  carriage  is  rare. 

Identity  of  Typhus  Strains.  —  There  has  always  been 
some  doubt  as  to  the  identity  of  Mexican  typhus  and  the 
typhus  of  Europe,  though  very  many  think  that  they  are 
one  and  the  same  disease.  In  his  early  experiments  Nicolle, 
in  Tunis,  was  not  able  to  infect  rhesus  monkeys,  but  only  the 
higher  apes,  while  the  experimenters  in  Mexico  found  the 
rhesus  susceptible;  but  later  Nicolle,  by  using  larger  doses, 
was  able  to  cause  infection  just  as  could  his  American  co- 
workers. No  experimental  difference  was  finally  noted  by 
the  two  groups  of  observers.  Recently  Brill  ^  has  reported 
cases  of  fever  occurring  in  New  York  for  many  years  which 
in  many  respects  resembled  typhus  fever  but  which  ap- 
peared to  be  much  milder  and  less  contagious.  In  New 
York  it  has  been  commonly  called  Brill's  disease.  Ander- 
son and  Goldberger,^  by  inoculation  and  immunizing  tests 
with  monkeys,  now  seem  to  have  shown  that  Brill's  disease, 
of  New  York,  and  Mexican  tarbadillo  are  identical.  If 
this  is  so  the  New  York  type  has  been  greatly  modified  or 
else  insect  carriers  are  rare  in  New  York,  for  the  disease 
shows  no  tendency  to  spread  in  either  the  family  or  the 
hospital. 

Dengue. 

Transmitted  by  Mosquitoes.  —  The  causation  and  mode 
of  transmission  of  dengue  are  somewhat  uncertain.  Graham 
believes  that  he  has  demonstrated  in  the  blood  a  protozoan 

1  Wilson,  J.  Hyg.,  Cambridge,  1910,  X,  155. 

2  Brill,  Am.  J.  M.  Sc,  Phil.,  1911,  CXLII,  196. 

^  Anderson  and  Goldberger,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv., 
Pub.  Health  Rep.,  1912,  XXVII,  149. 


410       THE  SOURCES  AND  MODES  OF  INFECTION 

which  he  considers  the  cause  of  the  disease,  but  his  findings 
have  not  been  substantiated.  Ashburn  and  Craig  ^  demon- 
strated that  it  is  possible  to  transfer  the  disease  to  healthy 
men  by  the  inoculation  of  blood  from  the  sick,  and  that  the 
virus  is  contained  in  the  filtered  blood.  They  also  proved 
that  the  disease  can  be  transmitted  by  a  mosquito,  Culex 
fatigans,  and  they  consider  that  this  is  probably  the  most 
common  mode  of  transmission.  Stitt  also  believes  that  the 
mosquito  is  the  bearer  of  the  disease.  Carpenter  and  Sut- 
ton could  not  transfer  the  disease  by  mosquitoes,  but  they 
did  not  experiment  with  C.  fatigans.  Ross  has  shown  that 
while  dengue  prevailed  elsewhere  in  Egypt,  there  was  none 
in  Port  Said  and  Ismailia,  where  the  mosquitoes  had  been 
exterminated.  Balfour,"  from  whose  review  this  information 
is  chiefly  taken,  states  that  in  Khartoum,  which  was  com- 
paratively free  from  mosquitoes,  especially  C.  fatigans,  there 
was  no  dengue,  though  persons  with  the  disease  in  all  proba- 
bility came  there  from  Port  Sudan  and  Haifa.  It  appears 
probable,  therefore,  that  the  contentions  of  Ashburn  and 
Craig  are  correct. 

Relapsing  Fever. 

Varieties.  —  According  to  Craig,^  there  are  at  least  four 
forms  of  relapsing  fever,  each  due  to  a  particular  kind  of 
spirocheta,  and  each  apparently  limited  in  geographical  dis- 
tribution. It  is  still  uncertain  whether  these  spirochete  are 
bacteria,  as  was  formerly  believed  and  as  is  strongly  urged 
by  Novy  and  Knapp,  or  protozoa,  similar  to  the  trypano- 
somes,  as  is  maintained  by  Schaudinn,  Prowazek,  Leishman 
and  others.  Whatever  they  may  be,  there  is  no  doubt  that 
at  least  one  form  of  the  disease  is  carried  from  person  to 
person  by  means  of  ticks. 

■  Ashburn  and  Craip;,  J.  Infect.  Dis.,  Chicago,  1907,  IV,  440;  also 
Philippine  J.  So.  [B.  Med.],  II,  93. 

^  Supplement  to  the  Third  Rop.,  Wellcome  Research  Lab.,  Khar- 
toum, 1908,  .37. 

»  Craig,  The  Malarial  Fevers,  New  York,  1909,  445. 


INFECTION  BY  INSECTS  411 

Ticks.  —  The  African  form  of  relapsing  or  tick  fever  is 
caused  by  S.  duttoni,  whicii  was  discovered  by  Button  and 
Todd,  and  also  by  Ross  and  Milne  in  1904,  the  first  named 
of  whom.  Button,  lost  his  life  while  studying  the  disease. 
Button  and  Todd  demonstrated  beyond  question  that  the 
disease  may  be  carried  from  man  to  man  by  a  tick,  Ornitho- 
dorus  mouhata,  and  their  observations  were  confirmed  by  Ross 
and  Milne  and  by  Breinl  and  Kinghorn.  It  was  also  shown 
that  the  disease  is  hereditary  in  ticks,  according  to  Mollers/ 
even  to  the  second  generation.  Unlike  the  malarial  parasites 
and  the  trypanosomes,  these  spirochetse  soon  disappear  from 
the  blood,  and  chronic  latent  infections  do  not  seem  to  exist. 
Koch,  however,  suggests  that  the  spirochetae  may  ultimately 
be  found  in  rats,  and  that  these  rodents  may  be  the  real 
source  of  this  disease,  as  they  are  of  plague.  The  tick,  how- 
ever, is  said  to  be  exclusively  a  human  parasite.  It  is  found 
in  the  floors  and  crevices  of  houses  and  native  huts,  where  it 
hides  during  the  day  and  feeds  at  night.  The  spirochetae 
undergo  a  certain  development  and  multiplication  in  the  tick, 
but  whether  they  pass  through  a  definite  cycle  of  develop- 
ment, like  the  protozoa,  is  not  known.  Ticks  have  been 
known  to  be  infective  for  a  year  and  a  half. 

Bedbugs.  —  Even  before  the  discovery  of  the  spirocheta  it 
was  suggested  that  the  bedbug  might  be  the  carrier  of  the  dis- 
ease, but,  according  to  Balfour,^  Breinl  and  Kinghorn,  and 
Todd  have  by  experiment  shown  that  this  is  probably  not  so. 

Less  is  known  about  the  other  forms  of  relapsing  fever. 
Tictin  in  1897  believed  that  the  recurrent  fever  of  Europe  is 
transmitted  by  the  bedbug,  and  he  claimed  to  have  demon- 
strated its  possible  transmission  in  this  way,  but  the  experi- 
ments were  not  entirely  satisfactory  and  have  not  been 
substantiated. 

^  MoUers,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1908,  LVIII, 
277. 

2  Supplement  to  the  Third  Report,  Wellcome  Research  Lab., 
Khartoum,  1908,  190. 


412       THE  SOURCES  AND  MODES   OF  INFECTION 

The  Indian  form  of  the  disease  is  caused  by  S.  carteri,  and 
has  been  much  studied.  Mackie  could  demonstrate  the  spi- 
rochetse  in  bedbugs  fed  on  relapsing-fever  patients,  up  to 
the  sixth  day,  but  he  found  no  evidence  of  their  increase. 
Of  fifty-three  bugs  found  in  a  fever  ward,  only  one  contained 
spirochetae.  He  also  placed  infected  bedbugs  in  cages  with 
six  monkeys,  and  only  one  of  the  monkeys  contracted  the 
disease.      Other  sources  could  not  be  excluded. 

Lice.  —  Recently  the  same  author  has  found  the  spiro- 
chetse  in  from  two  to  fourteen  per  cent  of  body  lice  found  in 
fever  wards,  and  he  showed  that  the  parasites  increased 
in  number  in  the  lice.  Sergent  and  Foley,  in  Algeria,  have 
made  observations  and  experiments  tending  to  implicate  the 
clothes  louse,  Pediculus  vestimenti. 

Rocky  Mountain  Fever. 

Transmitted  by  Ticks.  — ■  Rocky  Mountain  tick  fever  prob- 
ably appeared  in  Idaho  about  1885,  and  is  now  found  in 
Idaho,  Montana,  Washington,  Oregon,  Wyoming  and  Utah. 
It  is  an  acute  fibrile  disease  with  a  high  mortality,  usually 
exhibits  an  eruption  on  the  skin,  and  is  followed  by  immunity. 
According  to  the  investigations  of  Ricketts,^  the  disease  is 
transmitted  by  means  of  ticks,  probably  from  some  of  the 
small  wild  animals  of  the  country.  He  showed  that  it  is 
possible  to  transmit  the  disease  to  monkeys,  guinea  pigs, 
gophers,  chipmunks,  rock  squirrels  and  other  animals  by 
allowing  ticks  ( Dermacenter  andersoni)  to  bite  first  an  infected 
animal,  and  later  a  healthy  animal,  which  soon  becomes 
infected.  There  is  evidence  that  the  virus  of  the  disease 
develops  in  the  body  of  the  tick  and  is  transmitted  to  its 
offspring.  Ricketts  has  shown  by  inoculation  experiments 
that  the  virus  is  contained  in  the  blood  serum  of  infected 
animals,  and  he  recently^  reports  the  discovery  of  a  bacillus 
which  he  believes  to  be  the  cause  of  the  disease. 

1  Ricketts,  Rep.  St.  Bd.  Health,  Idaho,  1907-08,  88. 

2  Ricketts,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  379. 


INFECTION  BY  INSECTS  413 

Biological  Carriers  Distinguished  from  Mechanical  Carriers. 

— In  most  of  the  diseases  thus  far  considered  in  this  chapter 
the  parasite  which  causes  the  disease  passes  through  a  defi- 
nite cycle  of  its  existence  in  the  insect  as  well  as  in  man. 
The  insect  is  in  most  cases  the  true  host  of  the  parasite  and 
has  been  called  a  "  biological  carrier  "  of  disease.  Most  of 
the  parasites  transmitted  in  this  way  belong  to  the  protozoa. 
On  the  other  hand,  insects  may  be  merely  "  mechanical 
carriers  "  of  disease.  The  blood  which  contains  the  germs  of 
the  disease  may  be  carried  on  the  mouth  parts  of  the  insect 
and  inoculated  into  the  next  person  bitten,  just  as  it  might 
be  carried  on  the  point  of  a  lancet. 

Plague. 

Discovery  of  Bacilli  in  Fleas.  —  According  to  Nuttall,^ 
Ogata  in  1897  found  plague  bacilli  in  fleas  taken  from  the 
body  of  a  rat  dead  of  bubonic  plague,  and  this  observation 
was  confirmed  by  the  German  Plague  Commission  the  same 
year.  In  1898  Simond  noted  that  persons  who  handle  dead 
rats  not  rarely  die  of  the  plague,  but  he  found  that  infection 
never  occurred  if  the  rats  had  been  dead  over  twenty-four 
hours.  He  also  found  that  persons  with  plague  occasionally 
presented  on  their  skin  what  appeared  to  be  flea  bites,  and 
he  was  able  to  demonstrate  plague  bacilli  in  these  supposed 
bites.  He  was  able  also  to  demonstrate  plague  bacilli  in 
fleas  taken  from  rats  dead  of  the  plague. 

Plague  derived  from  Rodents.  —  Simond's  observations 
led  to  much  study  and  experiment  and  to  still  more  contro- 
versy. It  has  been  shown  by  large  numbers  of  observations 
that  plague  is  primarily  a  disease  of  the  lower  animals,  par- 
ticularly of  rodents,  many  species  of  which  easily  become 
infected.  It  has  been  shown  also  that  plague  in  man  is  gen- 
erally derived  from  the  same  disease  in  rats,  or  more  rarely 
mice,  and  recently  in  California  from  ground  squirrels  {CiteU 
lus  heecheyi). 

1  Nuttall,  Johns  Hopkins  Hosp.  Rep.,  Bait.,  1899,  VIII,  1. 


414       THE  SOURCES  AND  MODES  OF   INFECTION 

Epidemiological  Evidence.  —  The  very  careful  observa- 
tions of  Thompson'  in  Australia  showed  that  outbreaks  of 
human  plague  were  preceded  by  outbreaks  of  rat  plague, 
that  human  cases  were  connected  in  one  way  or  another  with 
foci  of  rat  infection,  and  that  the  dispersal  of  human  cases 
did  not  result  in  the  dispersion  of  plague.  He  showed  that 
while  human  plague  had  a  local  association  with  rat  plague, 
the  association  was  not  a  direct  one,  but  was  such  as  to  render 
necessary  the  assumption  of  some  such  intermediary  as  the 
flea.  It  also  seemed  to  him  that  the  location  of  the  buboes 
was  in  accord  with  the  theory  of  fiea  infection. 

Experimental  Work.  —  Objection  had  been  made  by  Nut- 
tall  and  others  to  the  flea  theory  on  the  ground  that  rat  and 
human  fleas  are  of  different  species,  but  Tidswell  in  Sydney^ 
showed  that  rat  fleas  when  hungry  will  bite  man.  This  has 
been  substantiated  by  many  other  observers,  some  of  whom 
have  also  shown  that  Pulex  irritans,  the  human  parasite,  will 
occasionally  bite  rats.  It  has  also  been  shown  that  fleas 
speedily  leave  a  dead  animal,  and  then,  impelled  by  hunger, 
they  attack  the  nearest  victim.  As  was  shown  by  Nuttall, 
plague  bacilli  may  live  in  fleas  for  several  days.  The  English 
Plague  Commission  found  as  many  as  5000  bacilli  in  the 
stomach  of  a  single  flea,  and  they  believe  that  they  increase 
in  number  for  a  while  and  sometimes  live  for  fifteen  days, 
but  in  starved  fleas  do  not  live  over  a  week.^  Verjbitski  *  has 
also  confirmed  these  observations.  He  has  shown,  too,  as  did 
Nuttall,  that  bedbugs  may  become  infected  and  harbor  the 
germs  for  some  days.  According  to  Tidswell,''  rats  are  fre- 
quently infested  with  bedbugs  (Cimex  lectularuis) ,  but  there 
is  no  evidence  as  yet  that  these  play  any  important  part  in 

»  Thompson,  Reports  of  Plague  in  Sydney,  1902  to  1907. 
^  Tidswell,  Rep.  on  Second  Outbreak  of  Plague  in  Sydney,  1902, 
73-75. 

»  J.  Hyg.,  Cambridge,  1907,  VII,  419. 

*  Verjbitski,  J.  Hyg.,  Cambridge,  1908,  VIII,  163. 

*  Loc.  cit. 


INFECTION  BY  INSECTS  415 

the  causation  of  the  disease.  Verjbitski  showed  that  if  the 
biting  insect  is  crushed  on  the  skin,  either  the  bite  or  neigh- 
boring scratches  are  easily  infected. 

Demonstrations  in  India.  —  Finally,  the  very  beautiful 
experiments  of  the  English  Plague  Commission^  showed  con- 
clusively that  infection  by  fleas  was  practically  the  only  way 
in  which  experimental  animals  could  be  infected  under  natural 
conditions.  These  experiments  have  been  referred  to  on 
pages  204  and  262.  In  one  experiment,  a  plague-infected  vil- 
lage was  cleared  of  its  human  inhabitants  and  guinea  pigs 
placed  in  the  houses,  and  it  was  demonstrated  that  infection 
took  place  only  through  the  medium  of  fleas.  The  experi- 
mental and  epidemiological  evidence  is  that  the  bubonic  form 
of  human  plague,  which  is  by  far  the  most  common  form,  is 
caused  by  the  transference  of  the  bacilli  from  rodents  to  man 
by  means  of  fleas. 

Plague  rarely  spread  except  by  Fleas.  —  While  it  is  true 
that  the  flea  is  the  chief  agent  in  the  transmission  of  plague, 
the  disease  may  possibly  be,  and  doubtless  occasionally  is, 
spread  in  other  ways.  In  experimental  animals  it  is  possible 
to  induce  it  by  the  ingestion  of  infected  food,  and  the  contact 
of  the  abraded  or  injured  skin  with  any  substance  containing 
plague  bacilli  may  result  in  infection.  The  pneumonic  form 
of  plague,  when  no  precautions  are  taken,  is  highly  contagious, 
for  the  sputum  contains  the  bacilli.  In  some  outbreaks  of 
plague  the  pneumonic  form  prevails.  In  some  localities  the 
overcrowding,  filth  and  habits  of  the  people  may  cause  con- 
tact infection  or  infection  by  food  to  assume  some  impor- 
tance, but  in  Western  Europe,  Australia  and  America  there 
can  be  little  doubt  that  plague  is  chiefly  a  flea-borne  disease. 

Measures  against  Plague.  —  Measures  against  the  plague 
ought,  then,  to  involve  the  isolation  of  the  sick,  particularly 
those  sick  with  the  pneumonic  form.     In  India  evacuation 

*  J.  Hyg.,  Cambridge,  1906,  VI. 

See  also  Summary  of  Work  of  Commission,  1908,  Calcutta,  Supt.  of 
Gov.  Printing. 


416       THE  SOURCES  AND   MODES  OF  INFECTION 

of  infected  villages,  that  is,  the  removal  of  the  population 
from  the  vicinage  of  the  plague  rat,  is  a  measure  of  value. 
Disinfection,  if  it  includes  the  killing  of  fleas  and  rats,  is  an 
important  measure.  Haffkine's  serum  has  been  found  to  pre- 
vent attacks  for  several  months,  and  its  general  use  is  often 
of  value  in  preventing  the  development  of  individual  cases. 
But  the  chief  anti-plague  measures  must  be  directed,  not 
against  the  flea,  but  against  rats  and  other  rodents.  The  most 
obvious  procedure  is  to  attempt  the  destruction  of  the  rats, 
but  thus  far  this  has  proved  to  be  a  rather  hopeless  under- 
taking. Poisoning,  trapping  and  destruction  by  infectious 
disease  have  proved  only  palliative  or  adjuvant  measures. 
In  Japan,  in  Australia  and  in  California  the  most  energetic 
rat  destruction  has  not  materially  reduced  their  numbers. 
Thompson  ^  says :  "Prevention  of  epidemic  plague  conse- 
quently lies  in  maintaining  a  distance  between  the  rat  and 
man.  The  requisite  separation  between  rat  and  man  will  be 
better  secured  by  improving  the  construction  of  buildings 
than  by  attempts  to  exterminate  the  rat."  In  Sydney  large 
sums  are  being  spent  in  rebuilding  wharves  and  warehouses 
so  as  to  render  them  rat-proof.  In  San  Franscisco^  every 
effort  has  been  made  to  prevent  the  growth  of  rats  by  cutting 
off  their  food  supply,  by  improved  scavenging,  and  by  pro- 
viding metal  garbage  pails  and  rat-proof  receptacles  for  all 
kinds  of  food  and  grain  likely  to  attract  rats.  But  the  chief 
effort  was  directed  to  rat-proofing,  by  the  use  of  concrete 
construction,  of  stables,  markets,  provision  and  produce  ware- 
houses and  wharves. 

Anthrax. 
Nuttall,  in  his  valuable  discussion  and  bibliography  of  the 
subject  of  insect  carriers  of  disease,^  cites  a  large  number  of 

1  Thompson,  Internat.  Cong.  f.  Hyg.  u.  Demog.,  Berl.,  1907,  III,  672. 

*  Eradicating  Plague  from  San  Francisco,  Rep.  of  Citizens'  Health 
Com.,  1909. 

»  Nuttall,  Johns  Hopkins  Hosp.  Rep.,  Bait.,  1899,  VUI,  1;  see  also 
Rep.  to  Local  Gov.  Bd.,  Lond.,  on  Pub.  Health,  1909,  n.  s.,  16. 


INFECTION  BY  INSECTS  417 

authors  who  suggest  that  anthrax  may  at  times  be  trans- 
mitted by  any  biting  insects  which  pass  from  cattle  to  man. 
Numerous  instances  are  given  of  persons  who  date  the  begin- 
ning of  their  pustule  from  the  sharp  sting  of  an  insect,  but, 
as  was  well  said,  it  is  probable  that  often  the  first  noticeable 
sensations  in  the  development  of  the  pustule  are  wrongly 
considered  as  due  to  the  bite  of  an  insect.  In  a  few  cases  a 
fly  was  felt  to  bite  and  was  killed,  and  on  the  spot  a  ma- 
lignant pustule  developed.  Most  of  the  score  or  more  of 
writers  quoted  urge  this  mode  of  infection  on  purely  a  priori 
grounds,  and  it  is  certainly  highly  probable  that  where 
anthrax  is  at  all  prevalent  among  animals,  and  biting  insects 
pass  from  the  lower  animals  to  human  beings,  the  disease  is 
sometimes  transmitted  in  this  way;  but,  as  has  been  sug- 
gested, if  this  happened  often,  the  disease  would  be  more 
common  than  it  is.  Certainly  in  England  and  the  United 
States  practically  all  human  anthrax  results  from  handling 
infected  material. 

Nuttall '  allowed  bedbugs  to  suck  blood  from  mice  infected 
with  anthrax,  and  then  caused  them  immediately  to  bite 
healthy  mice.  In  all,  136  infected  bugs  were  used,  but  in  no 
instance  did  they  transmit  the  disease.  In  six  instances  the 
bugs  were  crushed  while  biting,  but  these  experiments  were, 
Hke  the  others,  without  result.  Nuttall  also  made  a  few 
similar  experiments  with  fleas,  with  like  negative  results.  He 
found  that  anthrax  bacilh  remained  alive  in  bedbugs  only 
for  from  two  to  four  days,  and  died  off  even  more  quickly 
in  fleas. 

Nuttall  carried  on  similar  experiments  with  bedbugs  and 
chicken  cholera,  but  these  were  equally  unsuccessful. 

Septic  Infection. 

Nuttall  cites  Faure,  Paltauf,  Chrzaszczewski,  Joseph  and 
Berry  as  having  noted  instances  of  septic  infection  following 
the  bites  of  insects,  and  others  are  occasionally  noted  in  medi- 
^  Nuttall,  loc.  cit.,  13. 


418       THE  SOURCES  AND  MODES  OF   INFECTION 

cal  literature.     That  this  accident  should  sometimes  happen 
seems  very  probable. 

Typhoid  Fever. 

Dutton^  caused  bedbugs  to  bite  a  typhoid-fever  patient 
and  after  twenty-four  hours'  fasting  to  bite  two  other 
healthy  persons,  both  of  whom  developed  typhoid  fever  in 
twelve  and  fourteen  days  respectively. 

Insects  carry  Germs  on  Bodies.  —  The  insects  thus  far 
considered  inoculate  disease  by  means  of  their  bites,  but  it  is 
evident  that  some  diseases  may  be  carried  by  them  in  other 
ways.  If  infective  material  exists  in  considerable  quantity, 
and  is  accessible  to  insects,  they  are  almost  certain  to  get  it 
on  their  legs  and  bodies,  and  may  then  carry  the  germs  to 
other  human  beings.  The  chance  of  their  doing  this  varies 
greatly  with  varying  conditions.  If  the  insects  fly,  the 
danger  would  seem  to  be  much  greater.  If  the  infective 
material  is  large  in  amount  antl  freely  exposed,  as  typhoid 
excreta  in  privy  vaults,  the  danger  of  fly  infection  is  in- 
creased, and  it  is  also  greater  if  there  is  a  possibility  of 
infecting  food  which  insects  love  to  visit.  Flies,  particularly 
the  common  house  fly,  Musca  domestica,  have  been  most 
often  accused  of  thus  carrying  infection,  but  other  insects 
have  not  escaped  susi^icion. 

Cockroaches  and  Other  Insects.  —  Engelmann^  reports 
cockroaches  extremely  numerous  in  certain  houses  in 
Chicago  where  typhoid  fever  prevailed,  and  she  attributed 
the  spread  of  the  disease  to  these  insiH'ts.  Weber^  accuses 
various  species  of  Psocidoe  of  carrying  tubercle  bacilli  from 
cow  to  cow,  and  states  that  \w  demonstrated  the  germs  in  one 
of  these  insects  found  in  a  manger.  In  fact  any  "domestic" 
insect  with  power  of  active  locomotion,  and  of  filthy  habits, 
may  be  considered  as  a  possible  carrier  of  disease  germs. 

>  Diitlon,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  1248. 
2  iMifTcliuiinn,  Med.  News,  N.  Y.,  1903,  LXXXII,  225. 
'  WclxT,  N.  York  M.  .J.  [etc.],  19()(),  LXXXIV,  884. 


INFECTION  BY  INSECTS  419 

But  the  house  fly  is  undoubtedly  the  most  numerous  and 
ubiquitous  and  the  most  "  domestic  "  in  its  habits,  and  it  is 
rightly  suspected  of  playing  a  larger  part  as  the  mere  passive 
carrier  of  disease  germs  than  is  any  other  insect. 

Mayer  ^  states  that  some  ants  were  seen  to  pass  between 
cages  containing  mice,  some  of  which  were  sick  with  mouse 
typhoid  and  some  well.  The  well  mice  soon  developed  the 
disease,  and  agar  plates,  so  placed  that  the  ants  ran  over 
them,  showed  numerous  colonies  of  the  B.  murium  typhi. 

Flies  seen  to  carry  Infective  Material.  —  A  large  number 
of  observers,  noting  the  passage  of  flies  from  infected  matter 
to  human  beings  or  to  food,  have  become  convinced  that 
these  insects  are  important  carriers  of  disease.  According 
to  Nuttall,  Budd  as  long  ago  as  1862  considered  it  proved 
that  Egyptian  ophthalmia  is  carried  from  child  to  child  by 
the  flies  that  can  be  observed  in  great  numbers  crawling 
over  the  face  and  eyes.  Laveran  noted  the  same  conditions 
in  Biskra,  and  he  and  many  others  believe  that  oriental  sore 
is  spread  in  the  same  way.  Nuttall  also  cites  several  of  the 
earlier  writers  as  believing  that  anthrax,  cholera  and  plague 
are  transmitted  by  flies. 

Experimental  Work.  —  With  the  development  of  bac- 
teriology, experiments  began  to  supplement  conjecture,  and 
it  was  definitely  determined  that  bacteria  might  be  carried 
on  the  bodies  of  insects,  which  indeed  is  self-evident,  and 
also  that  they  might  in  a  living  state  pass  through  the 
stomach  and  be  voided  in  the  feces.  According  to  Nuttall, 
Raimbert,  Davaine  and  Ballinger  demonstrated  living 
anthrax  bacilli  on  flies  of  various  kinds  that  had  been  feed- 
ing on  infected  material.  Nuttall  himself  showed  that 
house  flies  could  carry  for  48  hours  living  plague  bacilli 
which  they  had  derived  from  material  they  had  fed  on,  and 
Hankin  showed  the  same  for  ants.  Nuttall,  ir-  the  mono- 
graph previously  cited,  reviews  the  early  literature,  and 
many  useful  references  as  well  as  accounts  of  original  work 
1  Mayer,  Munchen  med.  Wchnschr.,  1905,  LII,  226. 


420       THE  SOURCES  AND  MODES  OF  INFECTION 

are  to  be  found  in  Howard's^  recent  work  and  in  the  valuable 
reports  to  the  Local  Government  Board.^ 

Cholera  Spirilla  on  Flies.  —  In  1886  Tizzoni  and  Cattani 
caught  flies  in  a  cholera  hospital  in  Bologna  and  found  that 
cultures  made  from  them  showed  cholera  spirilla.  Sim- 
monds  made  similar  observations  in  Hamburg  in  1892. 
Macrae  in  India,  in  1894,  exposed  boiled  milk  in  different 
parts  of  a  jail  where  cholera  prevailed,  and  found  that  it 
became  infected  with  cholera  germs.  Tsuzuki,  in  1904, 
captured  cholera-infected  flies  in  a  house  in  Tientsin  where 
there  were  cases  of  the  disease.  Chantemesse  and  Gagnon 
have  shown  that  flies  may  carry  virulent  germs  for  17  and 
24  hours  respectively.  Maus^  says  that  cholera  spirilla 
were  found  on  several  bluebottle  flies  caught  in  infected 
houses  in  the  Philippines.  Graham-Smith*  in  eight  experi- 
ments could  recover  cholera  spirilla  from  the  legs  and  wings 
of  flies  only  once  later  than  5  days  after  infection.  Even 
in  the  crop  and  intestines  the  numbers  rapidly  diminished, 
all  cultures  after  48  hours  yielding  negative  results. 

Typhoid  Bacilli  on  Flies.  —  The  earlier  observers  were 
merely  content  to  show  that  flies  could  transfer  pathogenic 
germs,  and  made  little  attempt  to  show  in  what  way  and 
for  how  long  they  could  be  carried.  Thus  Manning^  and 
Buchanan^  caused  flies  to  walk  over  typhoid  feces  and  then 
over  Petri  plates  with  the  result  that  some  of  the  plates 
became  infected.  Firth  and  Horrocks^  showed  that  typhoid 
bacilli  could  be  carried  on  the  legs,  wings,  head  and  bodies 
of  flies  and  that  they  could  be  found  in  their  excreta  after 
the  insects  had  been  fed  on  infected  material,  but  they  did 

'  Tho  IIouso  Fly,  Disease  Carrier,  N.  York,  1011. 

2  Reports  on  Pul).  Health  and  Med.  Subjects,  Nos.  5,  IG,  40,  53. 

'  Mans,  Al)st.  Med.  News,  N.  Y.,  1<)()2,  LXXI,  318. 

'  Rei).  to  Loeal  Gov.  Bd.,  Lond.,  1910,  No.  40. 

'■>  J.  Am.  M.  Ass.,  CliieaRo,  1902,  XXXVII,  1291. 

«  Laneet,  Lond.,  1907,  II,  21(). 

'  Hril.  M.  J.  Lond.,  1902,  II,  930. 


INFECTION  BY  INSECTS  421 

not  consider  that  they  had  definitely  proved  that  the  germs 
passed  through  the  intestinal  tract.  Faichnie^  believes  that 
typhoid  bacilli  are  more  often  carried  in  the  intestines  of 
flies  than  on  their  legs.  He  bred  flies  in  earth  infected  with 
typhoid  feces.  From  the  intestines  and  from  the  excre- 
ment of  flies  so  bred  he  recovered  typhoid  bacilli  up  to  the 
sixteenth  day.  Similar  breeding  experiments  were  carried 
on  in  earth  impregnated  with  feces  containing  B.  paraty- 
phosus  A.  and  bacilli  were  obtained  from  the  flies  up  to  the 
tenth  day.  Graham-Smith^  fed  flies  on  syrup  containing 
typhoid  bacilli  and  endeavored  to  determine  the  persistence 
of  the  germs  on  their  feet,  in  their  intestines  and  in  the 
"  specks  "  or  excreta.  Bacilli  were  not  found  on  the  feet  or 
in  the  specks  longer  than  48  hours  but  were  recovered  from 
the  intestines  for  at  least  6  days.  Similar  experiments 
carried  on  with  B.  enteritidis  (Gartner)  showed  that  while 
the  bacilli  could  rarely  be  found  on  the  legs  they  could  be 
recovered  from  the  "  crop  "  and  intestines  up  to  7  days  and 
probably  longer.  Hewitt^  allowed  flies  to  walk  over  thin 
smears  of  typhoid  feces  and  then  kept  them  in  cages  for 
24  hours  and  after  that  allowed  them  to  walk  over  culture 
media.  No  typhoid  colonies  were  found  and  only  a  few  of 
B.  coli.  Similar  experiments  were  made  with  B.  prodigiosus 
with  negative  results,  though  the  germs  were  recovered 
from  the  feet  of  the  flies  after  12  hours.^ 

Typhoid  Bacilli  on  Flies  from  Infected  Places.  —  Hamil- 
ton^ in  Chicago,  and  Fricker  in  Hamburg,  in  the  same  year, 
recovered  typhoid  bacilli  from  flies  in  houses  where  there 
were  cases  of  the  disease.  Klein^  also  recovered  typhoid 
bacilli  from  flies  from  houses  where  there  was  typhoid  fever. 

1  J.  Roy.  Army  M.  Corps,  Lond.,  1909,  XIII,  672. 

2  Rep.  to  Local  Gov.  Bd.,  Lond.,  1910,  No.  40. 

3  Hewitt,  Quart.  J.  Micr.  Sc,  1909,  n.  s.,  LIV,  394. 
*  Ibid.,  403. 

s  Hamilton,  J.  Am.  M.  Ass.,  Chicago,  1903,  XL,  576. 
6  Hein,  Brit.  M.  J.,  Lond.,  1908,  II,  1150. 


422       THE  SOURCES  AND  MODES  OF  INFECTION 

Faichnie,  above  cited,  proved  the  presence  of  typhoid 
bacilh  on  flies  caught  in  barracks  at  Ramptee,  India,  where 
there  was  an  outbreak  of  the  disease,  and  later  he  reported 
finding  typhoid-infected  flies  on  nine  other  occasions  in 
various  locahties.  Bartarelh,^  in  studying  a  house  outbreak 
near  Turin,  found  typhoid  bacilh  on  8  of  120  flies  caught  in 
the  house  and  on  2  of  35  caught  in  the  yard.  On  the  other 
hand,  as  might  be  expected,  some  have  failed  to  find  the 
bacilli  under  similar  circumstances,  as  Buchanan  at  Glas- 
gow, Gorham  at  Providence  and  Gunn  at  Orange,  N.  J. 

Tubercle  Bacilli  carried  by  Flies.  —  Spillmann  and 
Haushalter  found  tubercle  bacilli  in  the  intestines  and  in 
the  dejecta  of  flies  that  had  fed  on  tuberculous  sputum. 
Hoffmann  found  tubercle  bacilli  in  2  of  4  flies  captured 
in  a  room  occupied  by  a  tuberculous  patient,  and  also  in 
the  excreta  of  flies  scraped  from  the  walls  and  furniture  of 
the  room.  Lord^  found  virulent  bacilli  in  flyspecks,  but 
could  not  induce  the  disease  by  causing  guinea  pigs  to 
breathe  air  drawn  over  infected  specks.  Hay  ward  ^  demon- 
strated living  bacilli  in  flyspecks  after  the  flies  had  been 
fed  on  sputum  in  such  a  way  as  to  preclude  the  possibility 
of  the  infection  of  their  feet  or  bodies.  Andre*  demon- 
strated tubercle  bacilli  in  the  excreta  of  flies  by  inoculation 
tests,  and  he  found  that  they  appeared  in  the  feces  about 
six  hours  after  feeding  and  continued  for  five  days.  Flies 
may  also  become  infected  by  eating  tuberculous  dust. 

Graham-Smith'''  after  feeding  flies  for  several  days  on 
syrup  infected  with  a  culture  of  human  tubercle  bacilli  de- 
termined that  the  bacilli  may  "  be  present  in  the  crop  for 
3  days.  In  the  intestines,  however,  tlu^y  may  be  found  for 
much  long(!r  periods,  being  present  in  considerable  numbers 

1  Centralbl.  f.  Bakteriol.  (etc.),  I,  Abt,.,  Jona,  1910,  LIII,  486. 

2  Lord,  lioslon  M.  &  S.  J.,  1904,  CLI,  651. 

»  Ilayward,  N.  York  M.  J.  [etc.],  1904,  LXXX,  64.3. 

*  AiuM;  ()th  Internal,,  (bn^.  on  Tuberc,  Wasli.,  1908,  I,  162. 

s  Grahani-Sniitli,  l{e|>-  '"  ^jocaiI  Ciov.  13d.,  1910,  No.  40. 


INFECTION  BY  INSECTS  423 

for  at  least  6  days.  Subsequently  their  numbers  diminish, 
but  they  may  be  discovered  by  careful  search  for  12  days 
or  even  longer.  In  the  faeces  they  are  numerous  up  to  the 
:fifth  day,  and  occasional  specimens  may  be  found  in  faecal 
material  deposited  between  the  sixth  and  fourteenth  days 
after  infection."  Flies  fed  on  sputum,  only,  contained  the 
bacilli  for  4  days,  but  flies  cannot  stand  forced  feeding  with 
sputum  as  they  do  with  infected  syrup. 

Anthrax  Bacilli  carried  on  Flies.  —  As  has  been  stated, 
several  early  observers  noted  the  ability  of  flies  to  transfer 
anthrax  germs.  Graham-Smith,  however,  has  shown  the 
period  during  which  the  flies  may  remain  infective.  He 
found  that  after  flies  have  fed  on  the  blood  of  an  animal 
dead  with  anthrax  the  spore-free  bacilli  do  not  remain  alive 
on  the  external  parts  of  the  fly  for  more  than  24  hours. 
They  may,  however,  persist  in  the  intestine  for  3  days  and 
in  the  crop  for  5  days.  When  flies  are  fed  on  anthrax  spores 
the  latter  do  not  develop  in  the  fly.  They  tend  to  disappear 
gradually  from  both  the  exterior  of  the  body  and  from  the 
intestine,  and  in  one  experiment  none  were  obtained  from 
legs  or  wings  after  the  tenth  day  and  from  the  crop  only 
once  after  that,  namely  on  the  sixteenth  day.  In  another 
experiment  the  spores  persisted  both  outside  and  inside 
the  fly  up  to  the  twentieth  day,  when  the  experiment 
terminated. 

Other  Disease  Germs  on  Flies.  Dysentery.  —  Auche^ 
allowed  flies  to  become  contaminated  with  cultures  of  the 
dysentery  bacillus,  and  found  that  they  could  carry  the 
germs  for  hours,  and  that  the  flies  would  take  up  the  bacilli 
from  feces  as  well  as  from  cultures. 

Graham-Smith  experimented  by  feeding  flies  on  an  emul- 
sion of  a  diphtheria  culture  and  showed  that  the  bacilli 
seldom  remain  alive  on  the  legs  and  wings  for  more  than  a 
few  hours,  but  may  live  in  the  alimentary  canal  for  24 
hours  or  even  longer. 

>  Auche,  Compt.  rend.,  Soc.  de  biol.,  Par.,  1906,  LXI,  450. 


424       THE  SOURCES  AND  MODES  OF  INFECTION 

He  also  made  use  of  the  Danysz  rat  virus:  "  A  number  of 
flies  were  allowed  to  feed  for  1  hour  on  a  broth  culture  of 
virus,  recently  recovered  from  the  body  of  a  rat,  and  were 
then  transferred  to  a  fresh  cage.  A  piece  of  bread,  soaked 
in  milk,  was  put  into  the  cage  daily  and  the  flies  allowed  to 
settle  and  feed  on  it.  After  1  hour  the  bread  was  removed 
and  given  to  a  mouse. 

"  A  mouse  was  also  fed  on  bread  soaked  in  milk  contain- 
ing an  emulsion  of  faeces,  passed  about  48  hours  after  in- 
fection, scraped  from  the  walls  of  the  cage.  The  animal 
died  in  2  days,  and  the  organism  was  isolated  from  it. 

"  These  experiments  show  that  flies  which  have  fed  on 
virus  are  capable  of  infecting  food  on  which  they  settle  and 
feed  to  such  an  extent  that  mice  fed  on  it  become  infected." 

According  to  Nuttall  and  Jepson,  Welander  found  that 
flies  could  carry  living  gonococci  on  their  feet  for  3  hours. 

Nuttall  showed  that  plague  bacilli  could  be  carried  by 
flies,  and  Graham-Smith  states  that  Yersin  in  Hong-Kong 
observed  dead  flies  lying  about  where  he  made  his  autopsies 
on  animals  which  had  died  of  the  plague  and  demonstrated 
that  the  flies  contained  virulent  plague  bacilli. 

Although  no  specific  germ  of  poliomyelitis  has  been  dis- 
covered the  infectivity  of  the  fluids  and  other  tissues  can 
be  tested  on  monkeys,  and  modes  of  infection  can  in  this 
way  be  studied.  Flexner  and  Clark ^  allowed  flies  to  feed 
on  the  fresh  spinal  cord  of  a  monkey  which  had  the  disease, 
and  determined  by  inoculation  that  the  virus  would  persist 
on  or  in  the  flies  for  at  least  48  hours.  Experiments  after  a 
longer  interval  were  not  tried. 

Mechanism  of  Infection  by  Flies.  —  Graham-Smith  has 
shown  that  flies  often  discharge  the  contents  of  their  crops, 
especially  wh(!n  fcnnling  on  dry  substances.  The  regurgi- 
tated material  frequently  contains  pathogenic  bacteria  for 
some  days  after  these  have  been  taken  up  by  the  flies.  Such 
bacteria  are  also  discharged  in  the  excrement.  The  germs 
•  J.  Am.  M.  Ass.,  ChictiKo,  1911,  LVI,  1717. 


INFECTION  BY  INSECTS  '425 

usually  do  not  live  more  than  a  day  or  two,  perhaps  less, 
on  the  legs  and  wings  but  persist  much  longer  in  the  ali- 
mentary tract.  Flies  allowed  to  walk  over  food  material 
may  infect  it  not  only  by  means  of  the  germs  on  their  feet 
but  also  by  the  matter  which  they  disgorge  when  they  stop 
to  feed  and  also  by  their  excrement.  There  is  less  chance 
of  infecting  liquids,  as  then  the  flies  do  not  need  to  disgorge 
to  soften  their  food.  Many  of  Graham-Smith's  experi- 
ments were  made  with  B.  prodigiosus  because  of  the  ease 
with  which  it  may  be  recognized.  Yet  in  his  experiments 
he  could  not  once  infect  milk  with  this  bacillus  either  by 
allowing  infected  flies  to  feed  on  it  or  to  drown  in  it. 

These  experiments  seem  to  show  that  while  infection  by 
flies  is  possible  it  is  not  as  easy  as  might  at  first  sight  appear. 
Nevertheless,  given  much  infected  material  and  large  num- 
bers of  flies,  it  is  entirely  conceivable  that  a  large  amount 
of  disease  may  be  caused  by  fly-borne  infection.  That  food 
may,  under  natural  conditions,  become  infected  is  shown 
by  the  observations  of  Macrae  in  regard  to  cholera.  In 
1899  the  writer,  with  the  assistance  of  Prof.  F.  P.  Gorham, 
exposed  agar  plates  and  dishes  of  milk  in  the  pantry  of  a 
house,  and  poured  large  amounts  of  a  culture  of  B.  pro- 
digiosus into  the  near-by  privy  vault.  Of  nine  tests,  four 
showed  infection  with  prodigiosus,  while  all  of  five  plates 
exposed  near  the  vault  were  so  infected.  Plates  covered 
with  wire  netting  were  not  infected.  Flies  were  very 
numerous  and  were  constantly  walking  over  the  plates. 

Such  a  mode  of  infection  is  also  indicated  by  the  observa- 
tions of  Vaughan,^  who  reports  that  during  the  Spanish  War 
flies  covered  with  a  white  coating  of  lime  were  often  seen 
crawling  over  the  food,  the  lime  showing  that  they  had  just 
come  from  the  latrines  where  lime  had  been  thrown  over 
the  fecal  matter. 

Wild  Flies  carry  Fecal  Bacteria.  —  Flies  caught  in  the 
open  have  been  shown  to  be  at  times  loaded  with  fecal  bac- 
1  Vaughan,  J.  Am.  M.  Ass.,  1900,  XXXIV,  1456. 


426       THE  SOURCES  AND  MODES  OF  INFECTION 

teria,  thus  indicating  at  once  their  habits  and  the  possibility 
of  their  carrying  certain  diseases.  Jackson^  found  as  many 
as  100,000  fecal  bacteria  on  a  single  fly,  and  as  a  general 
thing  the  nearer  the  flies  were  to  the  sewer  outlets  the  more 
numerous  were  this  class  of  bacteria.  Graham-Smith  ^  found 
fecal  bacteria  on  23.6  per  cent  of  148  flies  examined  in  Cam- 
bridge, England.  For  a  part  of  them  the  surface  of  the  body 
only  was  examined,  and  for  a  part  the  intestine  only.  Sur- 
face infection  was  about  two  and  a  half  times  as  frequent  as 
intestinal  infection.  The  highest  degree  of  infection  was 
found  among  flies  caught  near  decaying  animal  matter,  and 
the  next  highest  among  those  caught  near  manure.  Nash^ 
recovered  B.  coli  from  a  fly  caught  in  a  hospital  ward. 
Delepine*  found  bacilli  of  the  colon  type  in  four  of  thirty- 
five  collections  of  flies  caught  in  Manchester. 

More  Fecal  Germs  in  July  and  August.  —  Recent  obser- 
vations by  Torrey^  indicate  that  flies  may  be  more  dangerous 
late  in  the  summer.  He  found  that  fecal  bacteria  of  the 
colon  type  were  first  encountered  in  abundance  in  the  early 
part  of  July.  The  bacteria  in  the  intestines  of  the  flies 
were  8.6  times  as  numerous  as  on  the  surface  of  the  insects. 
On  the  surface  of  the  flies  the  colon-group  of  bacteria  consti- 
tuted 13.1  per  cent  of  the  total;  and  within  the  intestine 
37.5  per  cent  of  the  total.  Of  the  lactose  fermenters,  iso- 
lated and  identified,  79.5  per  cent  belonged  in  the  colon- 
aerogens  group  and  20.5  per  cent  in  the  acidi  lactici  group. 
Fifteen  cultures  of  streptococci,  isolated  and  identified, 
were  distributed  among  the  equinus,  fecalis  and  salivarius 
groups.     There  were  none  of  the  pyogenes  type.      Most 

1  Jackson,  Rep.  to  Com.  on  Pollution  [etc.],  of  the  Merchants'  Ass. 
of  N.  York,  1907,  16. 

^  Graham-Smith,  Further  Preliminary  Rep.  on  FUes  [etc.],  Rep.  to 
Loc.  Gov.  Bd.  on  Health,  n.  s.,  1909,  10. 

»  Nash,  J.  Ilyg.,  Cambridge,  1909,  IX,  141. 

*  Del<5pinc,  Rep.  on  Health  of  Manchester,  1906,  85. 

6  Torrey,  J.,  Infect.  Dis.,  Chicago,  1912,  X,  166. 


I 


INFECTION  BY  INSECTS  427 

important  was  the  isolation  of  three  colonies  of  B.  paraty- 
phosus,  A.  Bacteria  of  the  paracolon  type  causing  a  final 
intense  alkaline  reaction  in  litmus  milk  and  fermenting  only 
certain  monosaccharids  were  frequently  encountered  during 
August. 

Range  of  Flight.  —  As  stated  by  Howard,  probably  the 
distance  traversed  by  the  house  fly  varies  greatly  under 
different  circumstances,  being  greater  if  with  the  wind  and 
if  suitable  food  or  breeding  places  are  not  at  hand.  Howard 
cites  Forbes  as  observing  a  flight  of  half  a  mile  from  the 
tuberculosis  hospital  to  the  general  hospital  of  Cook  Co., 
111.  He  also  cites  Hine  as  finding  marked  flies  at  a  distance 
of  40  rods  on  the  third  day  but  never  as  far  as  half  a  mile. 
Austen  ^  after  liberating  marked  flies  found  them  at  dis- 
tances varying  from  300  to  1700  yards.  Under  the  direc- 
tion of  Delepine  300  flies  were  liberated  in  the  administra- 
tion building  of  a  hospital,  and  within  5  days  4  were  caught 
in  wards  distant  from  30  to  190  yards.  At  the  Worcester 
State  Hospital  Orton  and  Dodd^  observed  flies  carry  B. 
prodigiosus  from  the  laundry  to  the  kitchen  and  to  all  of 
the  wards  although  the  hospital  was  well  screened. 

Seasonal  and  Local  Distribution  of  Flies.  —  There  is  a 
disposition  in  many  quarters  to  rely  upon  a  study  of  the 
relation  of  fly  distribution  to  disease  to  throw  light  upon 
the  causative  relation  of  the  insects  to  the  disease  under 
consideration.  Such  studies  are  not  likely  to  prove  very 
convincing  and  they  are  of  little  value  unless  extensive. 
Proper  studies  of  the  seasonal  distribution  of  flies  have  been 
undertaken  in  only  a  few  localities  and  for  a  few  seasons. 
There  have  been  still  fewer  observations  on  the  local  dis- 
tribution of  the  insects  in  relation  to  the  local  distribution 
of  disease.  Even  if  a  quite  constant  correlation  of  seasonal 
fly  distribution  and  disease  distribution  is  determined,  the 
causative  relation  between  the  insects  and  the  disease  is 

1  Rep.  to  Local  Gov.  Bd.,  Lend.,  1911,  No.  53. 

2  Boston  M.  &  S.  J.,  1910,  CLXIII,  863. 


428       THE  SOURCES  AND  MODES  OF  INFECTION 

far  from  established,  as  both  phenomena  might  be  de- 
pendent on  some  other  cause. 

Species  of  Flies.  —  Various  species  of  flies  are  found  in 
and  about  houses  which  may  possibly  serve  as  the  mechani- 
cal carriers  of  disease.  Of  these  by  far  the  most  common  in 
dwellings  is  the  house  fly,  Musca  domestica,  though  other 
flies  are  not  infrequently  found.  In  New  York  Jackson 
found  that  98  per  cent  of  all  flies  captured  were  M.  domestica. 
In  London  in  1908  Austen  ^  found  that  next  to  the  house  fly 
the  most  common  species  were  Homalomyia  canicularis, 
Calliphora  erythrocephala  and  Muscina  stahulans.  In  Provi- 
dence in  1909  Sykes^  found  all  the  above,  and  also  consider- 
able numbers  of  Lucilia  ccesar,  Sarcophaga  sarracenice  and 
Stomoxys  calcitrans,  and  a  few  Scenopinus  fenestralis,  but 
99  per  cent  of  the  flies  caught  indoors  were  M.  domestica. 
The  bluebottle  fly,  Lucilia  ccesar,  has  been  accused  by 
Button^  of  transmitting  typhoid  fever.  Maus  in  the  Philip- 
pines blames  bluebottles  for  the  spread  of  cholera. 

Transmission  of  Disease  by  Flies.  —  Of  this  we  have 
very  little  actual  knowledge.  Because  flies  are  seen  to  pass 
from  sputum  and  feces  to  human  lips  and  to  food,  and 
because  it  is  shown  that  flies  may  carry  disease  germs  on 
their  bodies,  it  is  assumed  that  these  insects  are  the  frequent 
carriers  of  disease.  Again,  because  of  a  correspondence 
between  the  curves  of  fly  distribution  and  disease  preva- 
lence, though  this  correspondence  in  some  instances  is 
found  not  to  exist,  it  is  assumed  that  flies  are  a  prolific 
cause  of  sickness.  There  has  been  almost  no  experimental 
work  under  natural  conditions.  All  that  I  have  been  able 
to  find  are  the  two  negative  experiments  of  Peters,  to  be 
referred  to,  in  regard  to  summer  diarrhea.  To  determine 
with  any  degree  of  certainty  the  part  really  played  by  flies 
in  the  transmission  of  disease,  we  need  a  large  amount  of 

1  Austen,  Rep.  to  Local  Gov.  Bd.  on  Pub.  Health,  n.  s.,  1909,  No.  5. 

2  Sykes,  Rep.  Su[)t.  of  Health,  Providence,  1909,  13. 

3  Dutton,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  15G1. 


INFECTION  BY  INSECTS  429 

epidemiological  evidence  such  as  would  be  afforded  by 
changes  in  disease  incidence  following  control  of  the  fly 
nuisance.  At  present  there  is  very  little  of  such  evidence 
and  none  at  all  until  very  recently.  We  may  now  consider 
what  is  said  and  known  about  the  fly  carriage  of  certain 
diseases. 

Murrina. 

Due  to  Flies.  —  Darling  ^  has  reported  a  disease  occurring 
among  horses  and  mules  on  the  Isthmus  of  Panama.  It  is 
apparently  caused  by  a  trypanosome,  T.  hippicum.  Darling 
has  given  careful  attention  to  the  cause  of  the  disease  and 
is  satisfied  that  it  is  transmitted  by  a  biting  fly,  Stomoxys 
calcitrans.  He  has  never  been  able  to  demonstrate  the 
growth  of  the  trypanosome  in  the  body  of  the  fly,  and  he 
believes  that  the  disease  is  carried  mechanically.  He  does 
not  think  that  it  is  introduced  by  the  bite  of  the  insect  but 
only  through  abraded  surfaces  on  the  bodies  of  the  animals. 
Only  animals  having  superficial  sores  become  infected. 

Tuberculosis. 

Due  to  Flies.  —  Cobb  ^  watched  flies  passing  from  tuber- 
culous sputum  to  food,  and  he  attributes  to  these  insects 
a  large  proportion  of  tuberculosis  in  man.  Many  health 
ofiicials  and  anti-tuberculosis  leagues  have  issued  lurid 
bulletins  illustrating  the  agency  of  flies  in  transmitting  the 
germs  of  "  the  great  white  plague."  While  it  is  certainly 
possible  for  the  disease  to  be  transmitted  in  this  way,  there 
is  absolutely  no  evidence  that  it  is  a  factor  of  appreciable 
importance.  The  opportunities  for  infection  with  tubercle 
bacilli  in  other  ways  are  so  much  greater  and  more  numerous 
that  we  are  not  justified  in  considering  infection  by  flies  of 
much  importance. 

1  Darling,  J.  Infect.  Dis.,  Chicago,  1911,  VIII,  467. 

2  Cobb,  Am.  Med.,  Phila.,  1905,  IX,  475. 


430       THE  SOURCES  AND  MODES  OF  INFECTION 

Cholera. 

Due  to  Flies.  —  Cholera  has  of  late  been  considered  to  be 
to  a  considerable  extent  a  fly-borne  disease.  This  has  been 
the  view  of  Chantemesse  and  Borel/  as  well  as  of  many  of 
our  officials  in  the  Philippines,^  as  Heiser,^  Woodruff  "*  and 
McLaughlin/  though  all  of  the  latter  seem  to  consider  con- 
tact infection  a  good  deal  more  important  than  infection  by 
means  of  flies.  Nuttall  cites  Fliigge,  Macrae,  Buchanan 
and  Tsuzuki  as  considering  flies  of  great  importance  in  this 
disease.  Heiser®  says  that  cholera  was  spread  in  Bilibid 
prison  in  Manila  by  flies  passing  from  the  imperfectly  dis- 
infected latrines  to  the  food.  At  mealtime  they  were  seen 
to  pass  in  swarms  to  where  the  food  was  served.  After 
screening  cholera  ceased. 

Dysentery. 

Due  to  Flies.  —  In  a  recent  outbreak  of  dysentery  in  an 
asylum  at  Dan  vers,  Mass.,  involving  156  cases,  and  carefully 
studied  by  Ryder,^  flies  were  believed  to  be  the  chief  factor 
in  the  extension  of  the  disease.  In  1910  Orton  and  Dodd  * 
reported  an  outbreak  of  136  cases  and  22  deaths,  occurring 
in  July  and  August,  which  they  believed  must  be  due  to  flies, 
as  all  frank  cases  were  well  isolated,  screened  and  disin- 
fected. They  believed  that  contact  infection  from  these 
cases  was  out  of  the  question,  but  the  possibility  of  infec- 
tion from  carriers  does  not  seem  to  have  been  eliminated. 
The  buildings  were  well  screened,  but  many  flies  found  their 

'  Chantemesse  and  Borel,  Bull.  Acad,  de  mcd.,  Par.,  1905,  3  s.,  LIV, 
252. 

2  Maus,  Abst.,  Mcd.  News,  N.  Y.,  1902,  LXXXI,  318. 

3  Heiser,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  856. 

<  Woodruff,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  1160. 

6  McLaughhn,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1153. 

«  Heiser,  Bull.  State  Bd.  Health,  N.  Y.,  Sei)t.,  1911. 

-'  Ryder,  Boston  M.  &  S.  J.,  1909,  CLXI,  681. 

8  Orton  and  Dodd,  Boston,  M.  &  S.  J.,  1910,  CLXIII,  863. 


I 


INFECTION  BY  INSECTS  431 

way  in  nevertheless.  Dodd  ^  reports  much  the  same  con- 
ditions, though  with  only  99  cases  and  14  deaths,  in  1911. 
Dick^  states  that  dysentery,  in  which  both  Flexner  and 
Shiga  types  of  bacilli  were  present,  was  endemic  for  several 
years  in  an  asylum  at  Dunning,  111.  Flies  were  thought 
to  play  an  important  part,  and  the  disease  disappeared 
from  one  of  the  wards  after  screening  and  the  practice 
of  strict  medical  asepsis.  Hamer  ^  refers  to  an  outbreak  of 
dysentery  in  an  asylum  near  London  in  1906  alleged  to 
have  been  caused  by  flies. 

Diarrhea. 

Due  to  Flies.  —  Many  of  the  English  have  been  inclined 
to  attribute  considerable  influence  to  the  fly  as  a  factor  in 
the  causation  of  the  summer  diarrheas  of  infants.  News- 
holme,  who  believes  that  diarrhea  is  due  chiefly  to  infection 
of  the  milk  in  the  house,  says  that  opened  cans  of  condensed 
milk  are  often  seen  to  be  black  with  flies,  attracted  by  the 
sugar  in  the  milk,  and  attributes  to  them  no  inconsiderable 
share  in  the  causation  of  the  disease.  Sandilands,^  like 
Newsholme,  finds  diarrhea  especially  prevalent  among  the 
users  of  condensed  milk,  and  he  thinks  that  the  milk  is 
probably  infected  by  flies  after  the  can  is  opened.  Nuttall 
cites  Copeman  as  seeing  in  flies  the  possible  cause  of  an 
outbreak  of  diarrhea  investigated  by  him.  Nash^  in  1903 
stated  his  belief  that  the  house  fly  played  the  chief  part 
in  the  epidemiology  of  summer  diarrhea.  This  also  is  the 
view  of  Sandwith.^ 

Seasonal  Distribution  of  Diarrhea  and  Flies.  —  Obser- 
vations made  in  widely  different  localities  have  shown  a 

1  Dodd,  Boston  M.  &  S.  J.,  1912,  CLXVI,  211. 

2  Dick,  J.  Infect.  Dis.,  Chicago,  1911,  VIII,  386. 

'  Rep.  Med.  Off.  Health,  Co.  of  Lond.,  1907,  Append.  II. 

*  Sandilands,  J.  Hyg.,  Cambridge,  1906,  VI,  77. 

*  Nash,  J.  San.  Inst.,  Lond.,  190.3,  XXVI,  495. 
6  Sandwith,  Clin.  J.  Lond.,  1911,  XXXIX,  19. 


432       THE  SOURCES  AND  MODES  OF  INFECTION 

certain  relation  between  the  seasonal  distribution  of  flies 
and  summer  diarrhea.  Stations  are  established  at  various 
places  in  a  town  and  flies  are  caught  in  traps  or  by  means 
of  fly  paper,  and  the  number  of  flies  is  compared  with  the 
number  of  deaths  from  diarrhea.  Niven^  in  Manchester, 
in  1903,  found  that  the  "  fly  curve  "  and  the  curve  for 
diarrheal  deaths  corresponded  very  closely,  and  the  same 
agreement  was  noted  in  1905  and  1906.^  The  table  given 
by  him  shows  both  the  date  of  inception  and  the  date  of 
death  of  the  fatal  cases  of  diarrhea.  In  both  years  the  max- 
imum number  of  cases  occurred  at  almost  exactly  the  same 
time  as  the  maximum  number  of  flies,  and  the  maximum 
number  of  deaths  about  a  week  later.  In  1905  the  maxi- 
mum was  about  August  1,  and  in  1906  about  September  5. 
Robertson  in  Birmingham^  found  a  similar  correspondence 
in  that  city.  Jackson  in  New  York'*  showed  a  similar  close 
relation  between  flies  and  diarrhea,  as  has  Ainsworth^  for 
Poona  in  India.  Nash,^  showing  the  seasonal  distribution 
of  flies,  states  that  in  1902,  at  Southend,  there  were  few 
flies  and  little  diarrhea  in  August,  and  that  diarrhea  in- 
creased in  September  as  the  flies  increased.  Both  1902  and 
1903  had  cool  summers  with  few  flies  and  little  diarrhea, 
while  1904  and  1906  had  plenty  of  flies  and  plenty  of 
diarrhea.  In  1904  there  was  a  heavy  local  incidence  near  a 
large  dump  where  flies  abounded.  Hamer^  made  a  careful 
study  of  the  seasonal  distribution  of  flies  in  London,  and  he 
shows  that  while  there  is  an  apparent  agreement  between 
the  fly  curve  and  that  of  diarrheal  deaths,  the  latter  begins 
to  fall  before  the  former,  which  he  thinks  that  it  would  not 

»  Niven,  Rop.  on  Health  of  Manchester,  1903,  123. 

2  Rep.  on  Health  of  Manchester,  1906,  82. 

3  Robertson,  Rep.  Med.  Off.  Health,  Birmingham,  1910,  111. 

''  JacTvson,  Rep.  to  Com.  on  Pollution  [etc].,  of  the  Merchants'  Ass. 
of  N.  Y.,  1907,  17. 

s  Ainsworth,  J.  Roy.  Army  Med.  Corps,  Lond.,  1909,  XII,  485. 

«  Nash,  .1.  Hyg.,  Camhrid^ro,  1909,  IX,  141. 

">  Ilanier,  Rep.  Med.  OfT.  Ileallh,  Co.  of  l.oiid.,  1907,  Append.  II. 


I 


INFECTION  BY  INSECTS  433 

be  likely  to  do  if  flies  were  the  chief  cause  of  the  disease. 
Hamer^  in  a  later  report  shows  that  the  relation  between 
the  fly  curve  and  the  diarrhea  curve  varies  considerably  in 
different  years.  He  thinks  that  if  flies  have  any  part  in 
the  causation  of  diarrhea  it  is  much  obscured  by  other 
influences  and  that  too  great  importance  should  not  be 
attached  to  correspondence  in  any  one  year.  He  also  says 
that  the  period  of  maximum  infections  (not  dates  of  attacks) 
in  typhoid  fever  in  both  England  and  America  is  some  three 
weeks  later  than  in  diarrhea  and  that  this  is  not  reconcilable 
with  the  theory  that  the  seasonal  distribution  of  both  dis- 
eases is  determined  solely  by  the  distribution  of  the  fly. 

Maximum  of  Diarrhea  before  Maximum  of  Flies.  —  As 
regards  this  phenomenon  Peters^  has  suggested  that  it  is 
exactly  what  might  be  expected.  If  flies  are  the  chief 
factor  in  the  spread  of  diarrheal  disease  the  diarrheal  curve 
ought  to  lag  a  little  behind  the  fly  curve  in  the  early  part  of 
the  summer  outbreak,  for  the  increase  in  flies  approaches 
an  ordinary  arithmetical  progression  while  the  diarrheal 
increase,  he  says,  starting  from  an  amount  of  infection 
relatively  small,  but  proceeding  more  by  geometrical  pro- 
gression, later  on  rises  faster  than  the  fly  curve  and  reaches 
its  maximum  at  about  the  same  time.  The  fall  of  the 
diarrhea  curve  before  the  fly  curve  is  due,  he  believes,  to  the 
exhaustion  of  infection,  or  of  material  to  infect,  and  would 
doubtless  occur  even  if  the  fly  prevalence  continued  with- 
out a  decline.  A  general  agreement  between  the  fly  curve 
and  the  diarrhea  curve,  but  with  a  certain  definite  lack  of 
correlation,  is,  on  theoretical  grounds,  to  be  expected,  and 
Peters  states  that  just  this  correlation  exists  in  each  of  the 
eight  seasonal  charts  of  fly  and  diarrhea  distribution  pre- 
pared by  Niven  and  Hamer  before  referred  to. 

Problem  still  Unsolved.  —  Peters  in  this  paper  gives  the 
details  of  his  exceptionally  careful  and  valuable  epidemio- 

1  Hamer,  Rep.  Med.  Of.  Health,  Co.  of  Lond.,  1909,  Append.  IV. 

2  Peters,  J.  Hyg.,  Cambridge,  1910,  X,  602. 


434       THE  SOURCES  AND  MODES  OF  INFECTION 

logical  study  of  diarrheal  disease  in  Mansfield.  He  found 
that  many  of  the  local  conditions  were  well  explained  by  the 
fly  theory  of  transmission  and  that  no  facts  were  met  with 
which  were  directly  contradictory,  yet  he  arrives  at  no  more 
positive  conclusion  than  "  that  the  whole  question  merits 
the  most  thorough  and  laborious  investigation."  He  sug- 
gests that  a  "  positive  experiment  "  in  which  "  households 
duly  protected  against  all  other  chance  of  infection,  and  in 
which  flies  from  infected  houses  have  been  liberated,  de- 
velop abundant  diarrhea  "  would  afford  convincing  evi- 
dence. Such  an  experiment  he  tried  on  two  occasions 
without  positive  results.  He  also  suggests  "  negative 
experiments  "  to  determine  whether  screened  houses  in 
the  midst  of  infection  remain  free. 

Parallel  Seasonal  Distribution  not  Conclusive.  —  Al- 
though there  is  considerable  evidence  of  a  close  parallelism 
betweea  the  seasonal  distribution  of  flies  and  of  diarrhea, 
this  parallelism  is  no  proof  that  the  latter  is  dependent 
upon  the  former.  Even  as  corroborative  evidence  it  has 
little  value.  The  return  of  the  sun  from  the  equator  results 
in  a  great  variety  of  phenomena,  many  of  which,  though 
closely  related  in  time,  have  no  causative  relation  one  with 
another.  The  presence  of  flies  seems  to  be  closely  corre- 
lated with  the  temperature,  though  it  may  be  that  the  con- 
nection is  far  from  direct.  So  also  are  a  vast  number  of 
other  events  correlated  with  the  temperature,  though  they 
have  no  causative  connection  with  flies.  A  few  years  ago  it 
was  discovered  that  summer  diarrhea  developed  only  when 
the  temperature  of  the  soil  had  reached  a  certain  point,  and 
this  was  by  many  considered  a  demonstration  that  the 
germs  of  the  disease  d(>velopcd  in  the  soil.  Now  it  is  the 
fashion  to  say  that  diarrhea  is  due  to  flies  because  at  times 
the  increase  in  flies  ])recedes  by  a  little  the  increase  in 
diarrhea.  While  it  in;iy  l)e  that  flics  have  much  to  do  with 
the  causation  of  infantile  summer  diarrhea,  as  yet  we  have 
no  proof  of  it. 


I 


INFECTION  BY  INSECTS  435 

Local  Distribution  of  Flies  and  Diarrhea.  —  Jackson  in 
his  report  has  a  map  on  which  are  located  all  the  deaths 
from  intestinal  disease.  This  map  shows  that  the  great 
'  bulk  of  these  are  at  no  great  distance  from  the  water  front, 
where  the  flies  swarm  about  the  sewer  outlets.  It  is  just 
there  that  the  tenements  crowded  with  poor  children  are 
situated,  and  to  maintain  his  argument  it  would  be  neces- 
sary to  show  an  excess  over  and  above  the  excess  of  diarrhea 
always  found  in  tenements,  and  to  eliminate  the  other 
unfavorable  factors  associated  with  poverty. 

A  close  relation  between  an  excess  of  flies  in  a  neighbor- 
hood and  an  excess  of  diarrhea  has  not  been  found  by 
Davies  in  Woolwich,  Dudfield  in  Kensington,  Harris  in 
Isling"ton  and  Porter  in  Finsbury.^  Hamer  also  calls  atten- 
tion to  the  fact  that  among  English  towns  many  which  have 
a  very  high  typhoid  death  rate  have  a  low  diarrheal  death 
rate  and  vice  versa.  If  both  diseases  are  largely  dependent 
on  flies  this  needs  explanation.  In  our  own  country  Fall 
River,  which,  for  the  five  years  1904-1908,  had  a  death  rate 
from  typhoid  fever  of  13.2  (less  than  half  the  average  of 
the  registration  cities),  had  a  diarrheal  death  rate  of  380 
(over  three  times  the  average  of  the  registration  cities  and 
the  highest  of  all  of  them). 

Typhoid  Fever. 

Flies  in  Spanish  War.  —  More  attention  has,  however, 
been  bestowed  on  the  relation  of  the  fly  to  typhoid  fever 
than  to  any  other  disease.  Sedgwick  ^  was  the  first  that  I 
know  of  to  call  attention  to  the  importance  of  flies  as  a 
means  of  spreading  typhoid  fever,  but  the  excessive  typhoid 
death  rate  in  the  home  camps  of  our  soldiers  during  the 
Spanish-American  War  did  more  than  anything  else  to  call 
attention  to  the  possible  importance  of  the  fly  as  a  distrib- 
uter of  the  germs  of  this  disease.     Surgeon  General  Stern- 

1  Rep.  Med.  Of.,  Co.  of  Lond.,  1909,  Append.  IV,  7. 

2  Sedgwick,  Rep.  Bd.  Health  [etc.],  Mass.,  1892,  736. 


436       THE  SOURCES  AND  MODES  OF  INFECTION 

berg  had  issued  orders  to  guard  against  flies,  but  they  had 
little  effect.  Veeder  ^  clearly  set  forth  the  possibility  of  the 
transfer  of  fecal  matter  to  food  by  means  of  flies,  and  he 
declared  that  flies  were  the  principal  cause  of  the  prevalence 
of  the  disease  in  the  camps.  The  report  of  the  commission 
to  investigate  the  cause  of  the  fever,  although  laying  chief 
stress  on  contact  infection,  forcibly  emphasized  the  part 
played  by  flies  in  the  spread  of  the  disease.^  Vaughan,  a 
member  of  the  commission,  personally  urged  the  importance 
of  flies  in  the  spread  of  this  disease.^  Ever  since,  great 
popular  and  scientific  attention  has  been  bestowed  upon  the 
fly  in  the  United  States  and  also  in  other  countries. 

Other  Reports  of  Typhoid  Fever  due  to  Flies.  —  Nuttall 
cites  Quill,  Tooth  and  Calverly,  Smith,  Austen,  Straton  and 
Jones  as  attributing  much  of  the  army  typhoid  in  South 
Africa  and  India  to  the  presence  of  flies.  Numerous  writers 
on  typhoid  fever  in  civil  life  have  referred  to  the  fly  as  a 
most  active  agent  in  the  transmission  of  this  disease.  In 
"  The  House  Fly  at  the  Bar,"  published  by  the  Merchants' 
Association  of  New  York  in  1909,  are  printed  opinions  of 
seventy  or  more  health  officials  and  others,  all  but  nine  or 
ten  of  whom  are  emphatic  in  their  statements  that  flies  are 
very  important  carriers  of  disease  germs.  Some  few,  how- 
ever, consider  that  the  case  against  the  fly  has  not  been 
proved,  though  some  circumstances  are  suspicious.  Several 
give  instances  of  fly  infection  that  have  come  to  their  notice. 
Hurty  writes  of  an  outbreak  in  an  asylum  following  the  brief 
use  of  the  privy  by  a  walking  case  of  typhoid  fever.  Flies 
abounded  and  there  was  no  chance  for  contact.  Taylor,  of 
Denver,  reported  typhoid  fever  at  a  dairy.  The  milk  be- 
came inf(H'tetl,  he  thinks  by  flies,  for  the  privy  was  near  the 
milk  house,  and  gelatine  cultures  exposed  near  the  privy 

1  Vcodor,  Med.  Rec,  N.  Y.,  ISOS,  LIV,  429. 

^  Ab.st,.  of  Rep.  on  tlie  Orif^in  and  Spread  of  Typhoid  Fever  in  U.  S. 
Military  Camps  during  the  Spani.sh  War,  1898,  183. 

»  Vaughan,  J.  Am.  M.  Ass.,  Chicago,  1900,  XXXIV,  1451,  1496. 


I 


INFECTION  BY  INSECTS  437 

and  in  the  milk  house  showed  colonies  of  typhoid  bacilli, 
presumably  deposited  by  flies!  Dr.  H.  W.  Hill,  the  exceed- 
ingly cautious  epidemiologist  of  the  Minnesota  State  Board 
of  Health,  writes  me  that  from  his  observations  in  that  state 
he  "firmly  believes  that  flies  are  an  important  factor  in 
the  spread  of  typhoid  in  such  places  as  mining  and  lumber 
camps,  and  that  the  small  country  village  with  its  exposed 
outdoor  closets  parallels  the  camp  conditions  exactly." 
He  further  states  that  Wald  noted  that  in  a  certain  camp 
the  Italians  did  not  contract  the  disease  because,  as  he 
thought,  they  did  not  eat  between  meals,  while  the  Finns 
suffered  severely  because  they  kept  their  food  laid  out  on 
the  table  all  the  time,  where  it  was  exposed  to  innumerable 
flies,  and  helped  themselves  during  the  day  at  random. 

Pease  ^  refers  to  an  outbreak  of  50  cases  at  Castleton  from 
June  to  September  all  in  the  vicinity  of  a  yard  where  typhoid 
excreta  were  thrown  and  where  flies  abounded.  Button  ^ 
accused  bluebottle  flies  of  carrying  infection  from  the  feces 
of  a  carrier  to  4  other  members  of  the  family.  In  1906  an 
outbreak  of  typhoid  fever  near  London  was  thought  by 
Ransome  and  Young  to  be  due  to  swarms  of  flies  which 
bred  in  a  manure  dump  near  by.^  In  none  of  these  alleged 
instances  of  fly-borne  infection  are  other  modes  excluded, 
and  often  it  is  quite  as  probable  that  the  cases  were  due  to 
contact,  and  in  scarcely  any  of  them  is  there  more  than  a 
possibility  that  the  disease  was  caused  in  the  manner 
alleged. 

Numerous  bulletins  and  circulars  have  been  issued  by 
state  and  municipal  health  ofl&cials,  some  of  which  depict, 
in  exaggerated  language  and  with  extravagant  illustration, 
the  danger  to  be  feared  from  this  household  pest,  and  a  dis- 
tinguished entomologist  has  urged  that  the  familiar  name 
of  M.  domestica  be  changed  from  house  fly  to  typhoid  fly. 

1  Long  Island  M.  J.,  Brooklyn,  1910,  IV. 

2  Button,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  1561.  " 

3  Rep.  Med.  Off.  to  Lond.  Co.,  Council,  1907,  Append.  III. 


438       THE  SOURCES  AND  MODES  OF  INFECTION 

Flies  suspected  from  their  Habits.  —  The  chief  reason 
why  the  fly  is  beheved  to  be  the  carrier  of  diarrhea,  cholera 
and  typhoid  fever  are  that  flies  are  seen  to  pass  from  feces 
to  food;  that  they  have  been  shown  to  carry  fecal  bacteria, 
and  in  several  instances  the  specific  bacteria  of  cholera  and 
typhoid  fever;  and  that  they  often  swarm  in  unusual  num- 
bers at  times  and  in  places  where  there  is  an  exceptional 
prevalence  of  disease.  The  very  definite  observations  of 
Hamilton,  Fricker,  Klein,  Simmonds,  Bartarelli  Faichnie, 
Mann  and  Tsuzuki  as  to  the  finding  of  infected  flies  in  in- 
fected houses,  and  the  accounts  given  by  Veeder,  Vaughan, 
Tooth,  Smith,  Hill  and  others,  of  the  contamination  of  food 
by  flies  in  camps,  military  and  civil,  certainly  render  it 
probable  that  these  insects  do  at  times  cause  sickness,  and 
may  under  certain  conditions,  such  as  prevail  in  camps,  be 
an  important  factor  in  outbreaks.  But  these  observations 
are  far  from  a  demonstration  of  what  is  now  generally 
claimed,  that  flies  are  the  chief  factor  in  the  spread  of 
typhoid  fever,  and  perhaps  of  summer  diarrhea,  in  well- 
ordered  civil  communities. 

Dr.  Howard's  Views.  —  Howard  in  his  admirable  work 
on  the  house  fly,  before  cited,  devotes  174  pages  to  the 
"  Carriage  of  Disease,"  a  large  part  of  which  is  taken  up  by 
a  consideration  of  typhoid  fever;  he  quotes  many  of  the 
writers  referred  to  in  the  last  few  pages  of  this  book  and  also 
some  others  as  Wanhill  in  Bernmda,  and  Washburn  in 
Minnesota,  who,  noting  the  filthy  habits  of  flies  and  their 
seasonal  distribution  in  relation  to  typhoid  fever,  are  con- 
vinced that  flies  are  an  important  factor  in  the  causation 
of  this  disease.  Very  little  convincing  epidemiological  evi- 
dence is  offered.  Howard  apparently  bases  his  own  view 
on  this  matter  upon  the  habits  of  the  fly,  for  he  says  that 
"  the  correlation  or  non-correlation  of  the  curve  of  house 
fly  a})undanc(>  and  the  abundance  of  typlioid  has  prac- 
tically no  effect  upon  our  conclusions  as  regards  the  pos- 
sible transfer  of  the  disease  by  flies."     Howard  cites  as 


i 


INFECTION  BY  INSECTS  439 

significant  the  experience  of  Palmer  in  Georgia  who  offered 
to  care  for,  without  charge,  any  typhoid  patient  Uving  in 
a  fly-proof  house,  but  none  applied.  He  also  found  no 
secondary  cases  in  families  which  controlled  flies  as  directed. 
This  does  not  appear  to  throw  much  light  on  the  subject, 
for,  if  there  were  no  secondary  cases,  his  families  must  have 
been  wonderfully  well  trained  in  avoiding  contact  infection ; 
and  this  is  doubtless  the  complete  explanation. 

Seasonal  Distribution  of  Flies  and  Typhoid  Fever.  — 
As  the  seasonal  distribution  of  flies  has  been  studied  with 
reference  to  diarrhea,  so  has  it  been  studied  with  reference 
to  typhoid  fever.  Jackson,  in  his  report  to  the  Merchants' 
Association  in  New  York  before  referred  to,  gives  a  chart 
showing  the  seasonal  distribution  of  flies  in  New  York  and 
of  deaths  from  typhoid  fever,  the  latter  being  set  back  two 
months  to  allow  for  the  assumed  time  between  the  date  of 
infection  and  the  date  of  death.  Hamer  thinks  two  months 
is  too  long  a  time.  He  thinks  that  it  is  nearer  five  weeks. 
The  apex  of  the  typhoid  curve  corresponds  fairly  well  with 
the  apex  of  the  fly  curve,  but  there  is  a  rise  in  the  typhoid 
curve  in  February,  two-thirds  as  high  as  that  of  August, 
which  certainly  cannot  be  attributed  to  flies.  Ainsworth 
in  India  ^  states  that  at  Poona  the  maximum  admissions  of 
typhoid  fever  to  the  hospital  occur  about  one  month  after 
the  maximum  fly  catch.  Judging  from  Ainsworth's  paper, 
there  appears  to  be  great  seasonal  variation  in  the  number 
of  flies  in  Poona,  correlated  closely  with  the  temperature, 
as  with  us. 

In  Jacksonville  2  it  is  said  that  the  fly  curve  and  the 
typhoid-fever  curve  correspond  closely,  though  Dr.  Terry 
gives  no  figures  or  diagrams.  According  to  Howard  a 
similar  correlation  has  been  worked  out  by  Purdy  in  New 
Zealand  (1910)  and  Osmond  in  Cincinnati  (1909). 

1  Ainsworth,  J.  Roy.  Army  Med.  Corps,  Lond.,  1909,  XII,  485. 
»  Am.  J.  Pub.  Health,  1912,  II,  14. 


440       THE  SOURCES  AND  MODES  OF  INFECTION 

Evidence  against  Theory.  —  Niven  ^  found  that,  while  in 
Manchester  in  1903  the  maximum  number  of  flies  was 
caught  about  August  29,  the  maximum  number  of  cases  of 
typhoid  was  not  reached  until  November,  during  the  whole 
of  which  month  the  morbidity  remained  high.  In  1906  ^ 
there  was,  as  usual,  a  well-marked  maximum  of  flies  about 
September  1,  and  while  the  typhoid  morbidity  was  high  in 
September,  being  65,  it  was  somewhat  higher  in  October, 
and  there  were  46  cases  in  November  and  50  in  January 
and  only  21  in  July  and  23  in  August.  In  Washington,' 
in  1908,  the  maximum  fly  catch  was  for  the  week  ending 
June  24,  after  which  it  steadily  and  rapidly  decreased. 
The  maximum  of  typhoid  cases,  according  to  date  of  at- 
tack, was  in  the  week  ending  July  22,  but  instead  of  falling 
rapidly,  as  did  the  fly  catch,  it  continued  high  until  the 
middle  of  September.  There  certainly  is  little  parallelism 
between  the  two  curves.  The  commissioners  appointed  to 
study  the  disease,  and  who  make  the  report,  say  that  the 
evidence  is  quite  strong  that  flies  play  a  relatively  small  part 
in  the  spread  of  typhoid  fever  in  Washington. 

In  Providence  the  seasonal  distribution  of  typhoid  fever 
cases,  according  to  date  of  first  symptoms,  for  the  six  years 
1904-1909,  was  as  follows.  All  cases  due  to  milk  and  all 
certainly  contracted  out  of  the  city  are  excluded. 


Jan. 

Feb. 

Mar. 

Apr. 

May 

June 

45 

36 

26 

48 

49 

56 

July 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

80 

161 

133 

117 

96 

59 

According  to  observations  of  Sykes,  the  maximum  fly  catch 
out  of  doors  was  about  the  last  of  July,  when  it  began  to  fall 

'  Niven,  Rop.  on  Health  of  Manchostor,  1903,  123. 

»  Rep.  on  Healtli  of  Manchester,  1900,  G3,  84. 

»  U.  S.  Pub.  Health  &  Mar.  IIoh.  Serv.,  Ilyg.  Lab.  Bull.,  No.  52,  30. 


INFECTION  BY  INSECTS  441 

off  quite  rapidly.  The  observations  as  to  the  indoor  catch 
were  not  very  numerous,  but  it  seems  probable  that  the  flies 
go  indoors  in  greater  numbers  as  the  weather  grows  cooler  in 
September.  There  is  certainly  not  a  very  close  agreement 
between  the  number  of  flies  and  the  prevalence  of  typhoid 
fever.  It  is  scarcely  possible  that  the  typhoid  fever  develop- 
ing in  November  is  due  to  flies,  and  yet  there  were  96  cases 
in  November,  and  the  November  rate  is  higher  than  that  of 
any  other  month  except  August,  September  and  October. 
If  we  cannot  attribute  the  excess  in  November  to  flies,  why 
should  it  be  thought  necessary  to  attribute  the  excess  of 
the  preceding  three  months  to  flies?  I  can  see  nothing  in 
the  seasonal  distribution  of  typhoid  fever  in  Providence  to 
warrant  the  assumption  that  flies  are  an  important  factor 
in  its  causation. 

In  London, 1  while  the  typhoid  curve  and  the  fly  curve 
corresponded  fairly  well  in  1907,  in  1908  the  greatest  preva- 
lence of  flies  was  in  the  second  week  in  August,  while  the 
maximum  of  typhoid  fever  notifications  was  in  the  second 
week  in  November.  In  1909  there  was  only  a  slight  autum- 
nal rise  of  typhoid  fever,  the  maximum  being  in  January, 
while  the  maximum  fly  prevalence  was  in  August. 

Correlation  of  Typhoid  Fever  and  High  Temperature.  — 
I  have  been  able  to  find  only  the  very  few  observations  noted 
above  as  to  the  correlation  of  fly  distribution  and  typhoid 
fever,  and  these  few  do  not  indicate  that  there  is  any  reason 
to  assume  that  the  flies  stand  in  causative  relation  to  the 
fever.  The  very  careful  work  of  Sedgwick  and  Winslow^ 
shows  that  throughout  the  world,  and  in  both  hemispheres, 
there  is  a  distinct  relation  between  this  disease  and  the  sea- 
sonal rise  in  temperature.  These  authors,  though  they 
recognized  a  certain  amount  of  infection  by  flies,  explained 
the  autumnal  increase  in  typhoid  fever  as  due  to  the  direct 

»  Rep.  Med.  Off.  Health,  Co.  of  Lond.,  1907,  1908,  1909. 
2  Sedgwick  and  Winslow,  Mem.  Am.  Acad.  Arts  &  Sc,  1902,  XII, 
No.  5. 


442       THE  SOURCES  AND  MODES  OF  INFECTION 

and  favorable  action  of  high  temperature  on  the  Hfe  of  the 
bacillus  outside  the  body.  This  view  hardly  seems  tenable 
from  what  has  since  been  learned  of  the  life  habits  of  the 
bacillus,  and  I  think  is  now  no  longer  held  by  the  authors. 
It  is  the  custom  now  for  most  writers  to  attribute  to  flies 
the  chief  role  in  the  autumnal  excess  of  typhoid  fever,  but 
from  the  evidence  at  hand  it  seems  wiser,  while  admitting 
the  fact  of  seasonal  distribution,  as  determined  by  Sedg- 
wick and  Winslow,  to  await  further  study  before  attributing 
this  definitely  to  any  one  cause  or  group  of  causes. 

Epidemiological  Evidence,  Minnesota.  —  More  direct 
evidence  of  fly  carriage  is  offered  by  Hill.^  He  reports  three 
large  insane  hospitals,  with  1400  to  1800  patients  each, 
having  outbreaks  of  typhoid  fever  at  about  the  same  time 
in  the  summer.  In  one,  the  wards  of  the  institution,  though 
screened,  were  full  of  flics,  which  followed  the  food  from  the 
kitchen,  which  was  unscreened  and  swarming  with  the  in- 
sects. In  a  second  hospital  the  disease  was  confined  almost 
exclusively  to  the  men,  whose  dining  rooms,  and  wards  too, 
were  swarming  with  flies,  while  the  women's  side  was  com- 
paratively free.  In  both  these  institutions  the  outbreak 
continued  until  cold  weather.  In  another  hospital  the  flies 
were  so  numerous  that  when  they  settled  on  the  slender 
wire  supporting  the  electric  lamps  they  gave  it  the  appear- 
ance of  an  inch  rod!  The  management  determined  to 
exterminate  the  flies,  which  they  did,  and  though  it  was 
two  months  before  cold  weather,  no  more  cases  developed 
after  the  period  of  incubation  had  passed.  Such  a  bit  of 
evidence  is  not  conclusive,  but,  if  observed  often  enough, 
would  be  cumulative  and  would  indicate  a  real  causative 
relation  between  typhoid  fever  and  flies  as  can  no  amount 
of  watching  the  habits  of  flics  or  comparing  fly  curves  and 
typhoid  curves. 

Evidence  from  Jacksonville,  Richmond  and  Asheville.  — 
The  health  oflicers  of  the  two  cities  first  named  have  very 
>  Hill,  Rep.  State  Bd.  Health,  Minn.,  1911,  206. 


INFECTION  BY  INSECTS  443 

forcibly  called  attention  to  the  much  greater  liability  of 
infection  by  flies  in  the  comparatively  more  "  unsanitary  " 
cities  of  the  south  and  have  criticized  the  present  writer  for 
an  apparent  disregard  of  this,  and  it  is  true  it  must  be  ad- 
mitted that  a  large  part  of  what  is  here  written  about  the 
comparative  unimportance  of  nuisances  in  general  and  the 
fly  nuisance  in  particular  is  based  upon  conditions  studied 
in  the  cities  in  the  northern  states  and  in  England.  Ac- 
cording to  Terry/  Jacksonville,  with  its  large  numbers  of 
poorly  made  privies  and  enormous  swarms  of  flies,  has  in 
the  past  been  no  better  than  an  old-time  army  camp  as 
regards  conditions  favoring  the  spread  of  typhoid  fever. 
Late  in  1910  a  most  energetic  campaign  was  begun  against 
the  fly  and  for  the  construction  of  fly-proof  privies.  In  1911 
there  were  reported  only  142  cases  of  typhoid  fever  as 
against  321  for  the  same  period  of  1910.  Formerly  60  per 
cent  of  the  cases  had  been  in  the  privy  section  and  40  per 
cent  in  the  sewered  section,  though  the  distribution  of  the 
population  was  the  reverse  of  these  figures.  After  the  fly 
campaign  there  was  little  difference  in  the  incidence  of  the 
disease  in  the  sewered  and  unsewered  portions.  The  high 
typhoid  rate  of  several  Georgia  cities  showed  no  falling  off 
in  1911.  It  would  have  been  well  if  Terry  had  given  the 
typhoid  fever  figures  for  a  number  of  years  and  had  also 
shown  the  seasonal  distribution  so  that  it  might  be  seen 
whether  the  decrease  was  confined  chiefly  to  the  fly  season. 
Still  the  figures  as  they  stand  are  striking  and  call  for  con- 
tinued effort  along  the  same  lines.  Just  as  this  is  going  to 
press  the  Report  of  the  Board  of  Health  of  Jacksonville  for 
1911  has  come  to  hand  and  on  page  16  is  a  diagram  which 
shows  that  reduction  in  typhoid  fever  incidence  in  1911  was 
confined  to  the  May-August  period,  the  time  of  fly  prevalence. 
In  Richmond,  Levy  ^  has  been  carrying  on  an  energetic 
and   well-directed  campaign  against    typhoid  fever  since 

1  Terry,  Am.  J.  Pub.  Health,  1912,  II,  14. 
^  Levy,  Rep.  Health  Dept.,  Richmond,  1910. 


444       THE  SOURCES  AND  MODES  OF  INFECTION 

1907,  with  the  result  that  the  death  rate  per  100,000  fell 
from  nearly  50  in  the  preceding  five  years  to  24.1  in  1909, 
21.9  in  1910  and  17.8  in  1911.  In  1910  strong  effort  was 
made  to  prevent  fly  infection  by  screening  privies  and 
patients,  and  by  reducing  the  number  of  flies.  In  a  letter 
Dr.  Levy  states  that  the  number  of  flies  is  still  large  but 
that  the  screening  has  been  very  effective.  I  judge  that  he 
attributes  a  good  deal  of  the  typhoid  reduction  to  this,  but 
it  is  difficult  to  disentangle  this  factor  from  supervision  of 
cases,  instruction  of  attendants,  disinfection  of  excreta  and 
better  notification.  It  is  worth  noting  that  the  decrease 
does  not  seem  to  be  greater  for  the  summer  months  than  for 
the  winter  when  flies  can  scarcely  be  a  factor. 

In  Asheville,  N.  C,  so  Dr.  McBrayer  writes  me,  there 
was  a  reduction  in  typhoid  fever  cases  from  119  in  1910 
to  60  in  1911,  due  chiefly,  he  believes,  to  strict  control  of 
privies  which  are  now  required  to  be  made  fly-proof. 

Privies,  Flies  and  Typhoid  Fever.  —  That  an  excess  of 
typhoid  fever  is  found  in  cities  or  sections  of  cities  where 
there  are  many  open  privies  has  often  been  noted.  Of  late 
some  have  attributed  this  to  the  transference  of  infected 
matter  by  flies.  There  is  little  warrant  for  this  assumption, 
though  Terry  says  that  in  Jacksonville  after  the  screening 
of  the  privies  there  was  no  excess  of  typhoid  fever  in  the 
unsewered  parts  of  the  city.  But  meanwhile  an  active 
campaign  against  typhoid  fever  was  being  waged,  and  more 
cleanly  privies  and  better  care  of  cases  would  do  much  to 
prevent  contact  infection.  That  the  excess  of  typhoid 
fever  in  privy  districts  is  doubtless  largely  due  to  contact 
is  shown  by  the  fact  that,  as  has  recently  been  noted  in 
Providence,  localized  outbreaks  among  careless  people  using 
privies  have  occurred  out  of  fly  time.  In  Washington ' 
investigation  has  shown  that  in  the  fly  season  the  users  of 
privies  furnish  a  higher  percentage  of  typhoid  fever  as  com- 

»  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Lab.,  BuU.  78,  1911,  66, 
160. 


INFECTION  BY  INSECTS  445 

pared  with  the  users  of  water-closets  than  they  do  in  the 
winter  time.  The  percentage  of  cases  furnished  by  the 
users  of  privies  in  fly  time  was  13.3,  in  the  winter  7.7,  but 
the  figures  were  not  large.  It  was  also  found  in  Washington 
that  during  1908  and  1909  the  32  per  cent  of  the  population 
living  in  unscreened  houses  furnished  about  59  per  cent  of 
the  cases  occurring  in  the  summer  and  fall.  But,  as  the 
report  suggests,  people  living  in  unscreened  houses  are  more 
likely  to  have  other  unsanitary  surroundings  and  to  be  of 
careless  habits. 

Sykes'  investigations  in  Providence  showed  that  flies  are 
25  to  30  times  more  numerous  in  the  uncleanly  parts  of  the 
city  than  they  are  in  the  clean  parts,  and  the  differences  in 
the  indoor  catch  is  even  greater.  Though,  as  shown  above, 
there  appears  to  be  some  excess  of  typhoid  fever  in  the  fly- 
infected  and  privy-using  parts  of  cities,  the  difference  bears 
no  comparison  to  the  difference  in  fly  distribution. 

Unwise  to  Claim  Too  Much.  —  While  the  fly  is  a  nuisance 
and  it  is  highly  desirable  to  get  rid  of  it,  and  while  it  seems 
likely  that  it  is  to  some  extent  a  means  of  spreading  disease, 
it  is  extremely  unwise  to  make  definite  statements  that  it  is 
the  chief  source  of  diarrhea,  of  cholera  or  of  typhoid  fever, 
unless  we  have  very  exact  proof,  and  it  is  unwise,  unless 
such  proof  is  at  hand,  to  urge  large  expenditures  to  get  rid 
of  flies,  promising  thereby  the  eradication  of  typhoid  fever 
and  other  diseases.  If  it  should  chance  that  a  mistake  has 
been  made,  and  that  the  fly  is  not  the  chief  disseminator  of 
typhoid  fever,  and  the  disease  still  persists  after  the  fly 
has  disappeared,  we  need  not  be  surprised  if  the  public  fail 
to  take  us  seriously  when  we  advise,  on  knowledge  that  is 
well  established,  that  mosquitoes  are  the  sole  carriers  of 
malaria  and  yellow  fever;  that  escape  from  the  tsetse  fly 
means  escape  from  sleeping  sickness;  and  that  a  rat-proof 
city  will  be  a  plague-proof  city. 

Control  of  Flies.  —  As  flies  are  a  great  nuisance  and  a 
possible  source  of  danger  it  is  very  desirable  that  they 


446       THE  SOURCES  AND  MODES  OF  INFECTION 

should  be  eliminated  as  far  as  possible,  but  too  much  money 
should  not  be  expended  in  the  experiment  and  too  large 
results  should  not  be  promised.  Each  individual  family 
can  very  effectually  control  these  pests  by  good  screening 
and  the  use  of  fly  paper.  It  is  desirable  that  people  should 
be  educated  to  dislike  flies.  Chantemesse  says  that  the 
housewife  should  think  it  as  much  of  a  discredit  to  have 
files  in  her  house  as  bugs  in  her  bed.  Circulars  of  informa- 
tion may  be  distributed,  but  care  should  be  taken  to  avoid 
exaggeration  and  not  to  promise  too  much  either  as  to  the 
effectiveness  of  remedies  or  the  resulting  decrease  in  disease. 
We  know  even  now  far  too  little  about  the  habits  of  flies 
and  the  best  ways  of  attacking  them.  Packard  and  How- 
ard gave  us  our  first  definite  knowledge,  but  this  has  been 
much  extended  by  Newstead,'  who  showed  that  the  fly  is 
far  less  exclusive  in  its  choice  of  breeding  places  than  was 
supposed. 

Howard  in  his  "  The  House  Fly  —  Disease  Carrier  "  gives 
a  summary  of  our  present  knowledge  which  contains  much 
information.  The  recent  papers  by  Terry  and  by  Dodd 
previously  cited  recite  interesting  and  suggestive  experi- 
ences. It  appears  that  effective  scavenging  is  the  most 
important  means  of  getting  rid  of  flies.  If  yards,  streets 
and  vacant  lots  were  kept  clean,  market  refuse  removed 
promptly,  and  all  garbage  kept  covered,  there  would  be  an 
enormous  reduction  in  the  number  of  flies  about  dwellings. 
The  most  practicable  way  to  prevent  the  breeding  of  flies  in 
stable  manure  is  to  compel  its  removal  once  a  week.  Wher- 
ever it  is  possible  the  privy  vault  should  be  abolished. 
When  this  is  impossible,  the  fly-proof  privy  has  been  urged 
and  the  Federal  Government  has  issued  a  detailed  account 
of   how   one   may    be   economically    constructed.^      This 

'  Newstead,  Rep.  on  tho  Habits,  etc.,  of  the  House  Fly,  to  the  Health 
Committee,  T.ivorpool,  1907. 

*  Stiles  and  Lumsden,  U.  S.  Dept.  Agriculture,  Farmers  Bull.  463, 
1911. 


INFECTION  BY  INSECTS  447 

has  seemed  somewhat  visionary,  but  the  energetic  work 
done  by  the  health  officers  of  Richmond,  Jacksonville 
and  Asheville  show  that  by  means  of  constant  supervision 
it  is  possible  to  make  such  privies  effective.  The  question 
of  covering  food  in  markets  and  shops  to  protect  it  from 
flies  as  well  as  from  dust  has  been  much  discussed.  Slack  ^ 
in  an  excellent  paper  concludes  that  the  danger  from  this 
source  in  a  well-ordered  city  is  not  very  great,  but  that  for 
aesthetic  reasons  the  public  might  well  demand,  through 
ordinances  or  otherwise,  that  food  be  so  protected.  In  this 
opinion  the  writer  heartily  concurs. 

Summary.  —  After  this  brief  examination  of  the  evidence 
in  regard  to  the  role  of  insects  in  the  transmission  of  disease 
we  are  justified  in  the  following  conclusions: 

First.  It  is  certain  that  yellow  fever  and  malaria  are 
transmitted  solely  by  certain  mosquitoes,  and  that  by  con- 
trolling the  mosquitoes  it  is  possible,  even  under  very  un- 
favorable conditions,  to  eradicate  or  reduce  to  a  minimum 
these  two  diseases. 

Second.  It  is  highly  probable  that  the  relapsing  fevers 
are  transmitted  solely  by  certain  ticks,  sleeping  sickness  by 
the  tsetse  fly,  filariasis  by  the  mosquito,  pappataci  fever  by 
a  fly  and  typhus  fever  by  lice. 

Third.  The  bubonic  type  of  plague  in  human  beings 
is  usually  transmitted  from  rat  to  man  by  the  flea. 

Fourth.  It  is  probable  that  under  certain  conditions,  as 
in  military  and  civil  camps  and  in  filthy  communities  with- 
out sewerage,  insects,  especially  flies,  may  be  an  important 
factor  in  the  spread  of  the  fecal-borne  diseases,  but  there  is 
no  evidence  that  in  a  well-sewered  city  with  few  privies  the 
house  fly  is  a  factor  of  great  moment  in  the  dissemination 
of  disease. 

1  Slack,  Am.  J.  Pub.  Hyg.,  1909,  V,  159. 


INDEX 


PAGE 

Actinomycosis 366 

African  cattle  fever 122 

Air,  see  Sewer  air. 

bacillus  influenzae  not  carried  by 99-100 

tuberculosis  in 298-299 

bacteria  found  in 282,  298-301 

danger  of  infection  by 300 

expired,  free  from  germs 287 

infection  by,  thought  important 137 

conclusions 313-315 

experiments  with  anthrax 312 

Mediterranean  fever 311-312 

plague 281,  312-313 

not  impossible 281 

of  wounds  by 300-301 

pneumococcus  in 300 

pus-forming  bacteria  in 299-300 

swine  plague  bacilli  in 300 

Air-borne  anthrax 285-286 

chicken  pox 270,  280 

disease  in  hospitals 270-271,  279-280 

slight  evidence  of 286 

infection  indoors 282 

in  surgery 283-284 

reasons  for  belief  in 259-260,  283 

influenza  is  not 277 

malaria  is  not 384 

measles 272-280 

rubella 280 

scarlet  fever 270-273,  280 

out  of  doors 272-273 

small-pox,  cases  traced  to  other  sources 268-269 

conclusions 269-270 

evidence  against 266-269 

of,  in  United  States 264-265 

from  hospitals 260-270 

infection  of,  denied 263-270 

objections  to  theory 265-266 

tuberculosis 194,  202-203 

typhus  fever 281 

whooping  cough 280 

Amebse  dysenteriae,  carriers  of 118 

grown  on  culture  media 24 

in  soil 24 

in  well  persons 118 

on  vegetables 24 

449 


450  INDEX 

PAGE 

Amebse,  intestinal  parasites 112 

species  of 24 

Amebic  dysentery 24, 118 

American  hospitals 142-145,  279 

Anchylostoma,  see  Uncinaria,  Hookworms. 

duodenalis 186 

Anchylostomiasis,  due  chiefly  to  contact 186-187 

Animals,  diseases  of,  affecting  man 371-373 

spread  tuberculosis  by  licking  one  another 204 

Anopheles  mosquitoes  carry  malaria 382-383 

species  and  habits 385-386 

Anthracosis 306-307 

Anthrax,  a  dust-borne  disease 285-286 

an  air-borne  disease 285-286 

and  f omites 226-227 

insects 416-417,  423 

bacillus,  see  Bacillus  anthracis. 

due  to  food  infection 2,  365 

experiments  in  infection  by  air 312 

from  hair,  hides 227 

morocco  factories 3 

wool 227 

wool  refuse 3 

perpetuated  by  direct  contact 2 

soil  in  relation  to 2 

spores  in  dust,  hair,  hides,  wool 226-227 

spread  by  unrecognized  or  concealed  cases 2 

Antisepsie  medicale  in  French  hospitals 198,  278-279 

Antitoxin  may  favor  spread  of  disease 386-387 

Ants  carry  bacillus  murium  typhi 419 

plague  baciUi. 419,  424 

Aspergillus  destroys  mosquitoes 390 

Asylums,  bacillary  dysentery  in :■■•.■•  183-184,  430-431 

percentage  of  bacillus  diphtherite  carriers  in 90 

typhoid  fever  in 51-52,  442 

Atoxyl  to  prevent  sleeping  sickness 402 

Atypical  cases,  laboratory  evidence  of 123 

not  easily  distinguished  from  (carriers 130-131 

Babies'  Hospital,  gonorrhea  in 165-166 

Bacillary  dysentery,  carriers  of 67-69 

caused  by  contact 183-184 

(iulture  of  bacillus  in  eye 183-184 

in  camps 183 

in  institutions 183-184 

mild  cases  of 68-69 

Bacillus  anthracis,  see  Anthrax  spores. 

carried  by  flies 419,  423 

growth  in  ponds 3 

relation  to  the  soil 2,  4 

saprophytic  existence  of 2 

Bacillus  coli  communis  cause  of  diarrhea 367 

ill  (hist  of  schoolrooms 294 

on  the  hands 179,192 

on  roller  towel 192 


INDEX  451 

PAGE 

Bacillus  diphtherise  carried  by  flies 423 

carriers  in  family 89-90 

insane  asylum 90 

schools 90-94 

investigation  of,  in  Massachusetts. . .       83 

of... 82-99 

found  intermittently 98 

in  bread 26 

carriers,  varieties  of 83 

virulence  of 82,  84-86,  91-92 

clay 233 

convalescents 82,  84-85,  98-99 

dust 290,  294 

holy  water,  on  cups,  pencils,  drinking  glass.      192 

membrane 240 

milk 25,  26 

otitis 94-95 

pupils  cause  disease  in  teacher 98 

rhinitis 94-95 

rooms 233,  241 

scarlet  fever 86-88,  91,  96 

school  children 82-86,  88,  90-94 

soil 26 

sore  throat 93-94,  98-99 

well  persons 82-83 

life  of,  in  butter 251 

may  be  air-borne 289 

not  in  normal  throats 84-85 

on  coat 227 

drinking  glass 192 

fomites. 192-193,  227,  240-241 

virulence  of 240 

pencils 193,  233 

resistance  to  drying 233,  290 

saprophytic  existence  of 25 

Bacillus  dysenterise,  carried  by  flies 423 

cause  of  diarrhea 367 

in  carriers 67-69 

feces 24 

milk 15 

soil 23 

resistance  to  drying 234 

saprophytic  existence  of 23 

Bacillus  enteritidis,  cause  of  diarrhea 367 

(Gaertner)  in  ice  cream 250 

in  food  poisoning 58,  371 

sporogenes,  cause  of  diarrhea 367 

Bacillus  influenzae  in  droplets 298 

not  carried  by  air 99-100 

saprophytic 26 

persistence  of 100 

resistance  to  drying 238 

widely  distributed 100-101 

Bacillus  leprae  in  droplets 297 


452  INDEX 

PAGE 

Bacillus  morbificans  in  food  poisoning 371 

Bacillus  paratyphi,  cause  of  diarrhea 367 

in  feces 16 

food  poisoning 371 

not  found  in  healthy  persons 59-61 

Bacillus  paratyphi  A  in  carriers 58 

Bacillus  paratyphi  B  in  carriers 59 

Bacillus  pestis  carried  by  ants 419-424 

in  bodies  of  fleas 236 

convalescent  animals 69-70 

convalescents . 70 

cow  dung 23 

dust 290-291 

sputum 71 

infection  of  soil  by 22 

not  found  on  floors 235 

on  cotton  goods 228 

resistance  to  drying 235-236,  290-291 

saprophytic  existence  of 22 

Bacillus  prodigiosus  on  flies 425 

in  droplets 295-297 

sewer  air 284 

Bacillus  pullorum,  carriers  of 71 

Bacillus  tetani  in  blank  cartridges 6,  226 

dirt  of  floors 239 

gelatine 6,  284 

intestines  of  aniniuLs 5 

soil 6,239 

latency  of 106 

on  lamp  wi(;k 6,  226 

resistance  of . 6,  225-226 

saprophytic  existence  of 6 

Bacillus  tuberculosis,  carriers  of .• 103-105 

in  air 298-299 

butter. 364-365 

communion  cujjs 195 

droplets 295-296 

dust 292-293 

flies,  and  fly  sp(>cks 422-423 

lymphatic  glands 203 

milk 355-356 

nose  and  moutli 103-104,  193,  203 

railway  carriag(>s 292 

room 235,292 

tonsils 203-204 

tramcars 292 

latency  of ' 104-105 

may  be  ckist-l)orne 289-290 

[)ass  from  stomacli  to  lungs 305-308 

not  found  in  street  dust 292 

in  expired  air 287 

on  spirometer 195 

Hai)r()phytic 26 

so  resistant  as  believed 234-235 


INDEX  453 


Bacillus  tuberculosis,  on  a  glass 195 

dishes 195 

fomites 194-195,  241-242,  292,  293 

hands 193-194 

napkin  rings 195 

sidewalks 194 

telephones 195 

tongue 203 

perishes  in  Kght 234-235 

proportion  of  human  and  bovine  types.. .  3GO-361 

resistance  to  drying 234-235,  241-242,  291 

swept  from  sidewalk  by  dresses 194 

Bacillus  typhi  carried  on  fingers 169-170 

flies  and 420-422 

in  blood 34-35 

bones 35 

butter 16 

cerebro-spinal  fluid 35 

dead  animals 8 

dust 290 

feces 9,  34-36 

gall  bladder 35,  42 

ice 13,  319,  340-341 

kidneys 35 

milk 15 

ovaries 35 

oysters 13 

privy  vaults 9-10 

prostatic  fluid 37 

seltzer  water 13 

seminal  vesicles 37 

septic  tank  effluent 10 

sewer  air 284 

soft  drinks 13 

soil 7, 10 

epidemiological  evidence  of  growth 16 

spleen 35 

sputum 37-38 

tidal  mud 8 

tonsils 34 

urine 37 

persistence  of 10 

water 10-13 

epidemiological  evidence  of  growth 17 

modes  of  contamination 320 

recovered  from 319 

increase  in  milk 17 

intermittent  excretion  of 46-47 

moisture  necessary  to  growth  of 16 

on  blankets 227 

vegetables 8 

path  of  entrance 34, 178 

resistance  to  drying 232-233,  290 

saprophytic  existence  of 7, 16 


454  INDEX 

PAGE 

Bacteria  and  sewer  air. 284-285,  288-289 

cultured  Jess  resistant  than  uncultured 11 

effect  of  drying  upon 231-232 

found  in  air 298-301 

inhalation  of ........ 304-305 

not  found  in  expired  air 287 

given  off  from  moist  surfaces 287, 288 

of  suppuration,  see  Pus  bacteria. 

on  cups 192-193 

fomites 239-242 

hands 192-194 

money 223-224 

pencils 192-193 

Bagging,  yellow  fever  from 213 

Balantidium 112 

Ballast,  yellow  fever  from 213 

Bathing,  typhoid  fever  from 324-325 

Baths,  public,  encourage  cleanliness 211 

Bed  clothing,  bacillus  diphtheria.^  on 240 

Bed,  smallpox  from 214 

Bedbugs  and  anthrax 417 

kala-azar 402 

plague 414 

relapsing  fever 411-412 

typhoid  fever 418 

Bedpan  carries  dysentery  ameba} 183 

Betel  nut,  cholera  spread  by 185 

Biological  carriers  distinguished  from  mechanical  carriers 413 

Black-leg 4 

Blank  cartridges,  bacillus  tctani  in 6 

Blankets,  bacillus  typhi  on 227 

Blood,  bacillus  typhi  in 34-35 

infection  of,  cause  of  typhoid  fever 34-35 

meningococcus  in 73 

yellow  fever  virus  in 393-394 

Boer  War,  typhoid  fever  from  dust  in 275-276 

flies  in 436 

Books,  bacillus  tuberculosis  on 241 

scarl(;t  fever  from 215 

Boophilus  annulatus  and  cattk'  fever 112 

liotryomyoosis 366 

liovinc!  tuberculosis  bacillus  may  infect  man 353-354 

Bread,  bacdllus  diphtheria)  in 26 

lirill's  disease 409 

liroad  Street  well 310-317,  325 

15rush,  ba(;illus  dipiitheriai  on 240 

Jiubonic  plagu(%  see  Plague. 

Butter,  a  source;  of  diplillieria 350 

bacillus  tuberculosis  in 364-365 

tyi)lii  ill 16 

life  of  bacillus  diphtheria'  in 251 

Calliphora  erylliroccphala 428 

Cam{)S,  baciilary  dysentery  in 183 


INDEX  455 

PAGE 

Camps,  filthy  condition  of 180 

typhoid  fever  in.  ....... 170-171,  435-437 

Caps  and  gowns  to  pi*event  infection 218 

Carbolic  acid  in  well  water 324 

Carriers  a  recent  discovery 33,  38 

source  of  protozoan  disease 126 

and  mild  cases,  number  of 124-125, 133-135 

cause  cattle  fever 112 

cerebro-spinal  meningitis 74-81 

cholera 65-67,  185 

diphtheria 94-99 

glanders 99 

malaria 114-115 

nagana 113 

typhoid  fever 47-54 

definition  of  and  classification  of 38-39 

during  incubation 39 

evidence  against 55 

of  infectivity 127-131 

explain  spread  of  cerebro-spinal  meningitis 78-81 

in  bacterial  diseases 127 

in  institutions 50-52,  65,  67 

infect  food 47-51,  60,  65 

milk 52-54 

intermittent  excretion  in 46,  62 

laboratory  evidence  of 123 

less  infective  than  the  sick 155 

more  dangerous  than  things 225 

not  always  dangerous .* 129 

of  amebic  dysentery 118,  183 

bacillary  dysentery 67-69 

bacillus  pullorum 71 

cattle  fever 112 

cerebro-spinal  meningitis 72-81 

cholera 61-67 

diphtheria,  importance  of 149-152 

dourine 113 

glanders 99 

gonorrhea 102 

influenza 99 

lepra  bacilli 105 

malaria 114-115 

measles Ill 

Mediterranean  fever 72 

nagana 113 

paratyphoid  fever 58-61 

plague 69-71 

pneumococcus 101-102 

poliomyelitis 118-121 

pus  organisms 105-106 

scarlet  fever 109 

sleeping  sickness 115-116 

smallpox 109-110 

tetanus  bacilli 106 


456  INDEX 

PAGE 

Carriers  of  tubercle  bacilli 103-105 

typhoid  fever 38-55 

among  different  classes 39-44 

cannot  be  isolated 152 

diu'ation  of  infection 45 

Vincent's  angina 117 

relation  to  infectivity 125 

shade  into  missed  cases  and  atypical  cases 130-131 

virulence  of  germs  in 126 

Cartridges,  bacillus  tetani  in 226 

Cattle  fever. 112,  122 

Celery,  typhoid  fever  caused  by 379 

Cerebro-spinal  meningitis  an  accident  of  infection 81 

carriers  of 73-81 

explain  spread  of 78-81 

contagiousness  of 79-80 

due  to  pneimiococcus 81 

infection  by  carriers 74-81 

isolation  a  failure  in 81,  146 

path  of  infection 73 

prompt  isolation  in,  a  success 146 

secontlary  cases 79-80 

Charbon  symptomatique 4 

Charts,  bacillus  tuberculosis  on 241-242 

Chicken  pox  air-borne 270,  280 

Chicks,  white  diarrhea  of 71 

Children  not  cleanly 190 

Cholera  and  contact 184-185 

flies. 420,  430 

fomites 215 

atypical  cases 65 

caused  by  washing  soiled  linen  in  running  streams 325 

from  betel  nut 185 

carriers 65-67, 185 

clotlung 215 

handling  food 185 

rags 222 

shellfish 374 

soil 20 

unrecognized  cases 20,  65 

water 325-326 

wells 325-326 

infection  of  nurses 185 

not  dust-bonui 289-290 

on  shipI)oard  due  to  infected  water 326 

outl)reaks  in  various  places 20 

spirillum,  see  Spirilhiin  cliolerie. 

Cliri.stmas  presents,  dipliMicria  from 215 

(Jiiiicx  le(;tularius,  sec;  liedbug. 

( 'ifcllus  beech(^yi 413 

( 'lams,  typlioid  fever  from 375 

('lay,  oaeillus  diphtlieri;!'  in 233 

Cleanliness,  education  in,  needed 208-209 

municipality  should  encourage 210-211 


INDEX  457 

PAGE 

Cleanliness,  neglected 206-208 

rare 178-180 

in  children 190 

teaching  of,  in  school 209-210 

versus  disinfection 257 

Cloth,  yellow  fever  from 213 

Clothing  as  fomites 216 

bacillus  tuberculosis  on 242 

cholera  from 215 

infection  by,  rare 217-219 

leprosy  in 216 

scarlet  fever  not  from 217 

typhoid  fever  from 219 

typhus  fever  not  from 216-217 

Coat,  bacillus  diphtherise  on 227 

scarlet  fever  from 215 

Cockles,  typhoid  fever  from 375-376 

Cockroaches  and  disease 418 

Colon  bacillus,  see  Bacillus  coli  communis. 

Communion  cups,  bacillus  tuberculosis  in 195 

individual,  adopted 210 

Conductors  not  infected  by  money 224 

Connorrhinus 403,  404 

Contact  by  drinking  cups 189-190,  192-193 

chief  mode  of  infection 195-206 

indirect,  vehicles  for 188-190 

infection  and  fingers 188-189 

disregard  of 207-208 

importance  of 206 

in  amebic  dysenterj' 183 

bacillary  dysentery 183-184 

cerebro-spinal  meningitis 73-74,  76-77,  80 

cholera 184-185 

diarrhea 185 

diphtheria 196-202 

gonorrhea 165-167 

influenza 277 

measles 199 

Mediterranean  fever 312 

scarlet  fever 19G-202 

syphilis 164,  167-169 

tuberculosis 204-205 

typhoid  fever 17,  47-50,  169-183 

amount  of 177-178 

evidences  of 177 

in  civil  life 171-173 

in  hospitals 198-202 

opportunities  for 179-180 

role  of  privies 180-182 

Spanish  war 170 

why  disregarded 179-181 

uncinariasis 186 

less  easy  in  some  diseases  than  in  others ....  187-188 
most  obvious 164 


458  INDEX 

PAGE 

Contact  infection,  opportunities  for.  .... 190-192 

mode  of  infection  between  families 196-198 

with  missed  cases,  importance  of 190-192 

well  carriers,  importance  of 191 

Contacts,  diphtheria  carriers  among 89 

typhoid  carriers  among 43 

Contagiousness,  factors  involved 153-155 

less  outside  family 154-155 

than  beUeved 153-155 

of  carriers  less  than  that  of  sick 155 

Convalescents,  cholera  spirilla  in 61-65 

diphtheria  bacilli  in 84,  85 

dysentery  amebse  in 118 

bacilhin 68-69 

malarial  parasites  in 114-115 

meningococci  in 74-77 

plague  bacilli  in 70-71 

pneumococci  in 101 

typhoid  bacilli  in 40-41 

Cornet,  diphtheria  from 215 

Cotton  goods,  bacillus  pestis  on 228 

smallpox  from 214 

Cow  dung,  bacillus  pestis  in 23 

Cows,  diphtheria  in 347 

scarlet  fever  said  to  occur  in 346-347 

Crawfish  and  typhoid  fever 378 

Cream,  typhoid  fever  from 349 

Cubicles  for  isolation  in  French  hospitals 198-200 

Culex,  experiments  with 383 

fasciatus  and  yellow  fever 392 

fatigans  and  dengue 410 

filariasis 399 

Cuhcides 388-389 

mosquil  o  destruction  by 390,  397 

Culture  method  of  diagnosis,  introduction  of 137-138 

Cups,  bacteria  on 192-193 

Danysz  rat  virus  carricnl  by  flies 424 

Dead  animals,  bacillus  tyi)hi  in 8 

bodies,  spirillum  cholera;  in 19 

Dengue  transmitted  by  moscjuitoes 409 

Dermacenter  andcrsoni 412 

Diarrliea,  bacteria  which  cause 367 

due  to  condensed  milk 368-369 

contact 185,  367 

dust 276-277 

flies 431-435 

milk 366-369 

not  always 185 

water 327-329,  331,  334 

explosive  outbreaks 369 

nature  of 366-367 

prevention  of 369-370 


INDEX  459 

PAGE 

Diarrhea,  relation  of  feeding  to 367-369 

white,  of  chicks 71 

Diphtheria,  atypical 92-94, 133 

baciUus,  see  Bacillus  diphtherise. 

carried  to  homes  by  discharged  scarlet  fever  cases ...       98 

carriers,  importance  of 149-152 

isolation  of,  often  impossible 150-152 

chronic 99 

cultures  introduced 137-138 

value  of  findings 84-85 

disinfection  imnecessary  after 247-250 

extension  in  dweUings 197-198 

family  infection 89-90 

from  butter 350 

carriers 95-99 

Christmas  presents 215 

cornet 215 

drinking  glass 192-193 

fomites 215-227 

milk 96-97,  346-347 

pitcher 97 

sewer  air 273 

teacher 97 

tools 215 

in  cows 347 

Owatonna,  Minn 144 

Providence 136,  138 

Willard  State  Hospital 144 

isolation,  dm-ation  in  Providence 143 

in  institutions,  failure  of 143-145 

principles  of 149-152 

mild  cases  found  by  cultures 138 

not  air-borne  in  hospitals 273-274 

dust-borne 290 

from  soil 28 

of  extra-corporal  origin 29 

similarity  to  scarlet  fever 106-107 

warning  sign  in - 151 

with  recurrent  ear  discharge  causes  infection 98 

Disease  rarely  carried  by  physicians 217 

Dishes,  bacillus  tuberculosis  from 195 

Disinfection,  American  views  on 256 

desirable  at  times 256-257 

EngUsh  views  on 255-256 

French  views  on 255 

in  Providence 137 

abandoned 247-252 

schools 254 

objections  to 257 

of  Uttle  value 247-256 

unnecessary  after  diphtheria 247-250 

in  other  diseases 252-254 

scarlet  fever 250-252 

versus  cleanliness 257 


460  INDEX 

PAGE 

Dog  drinks  from  the  drinking  glass  on  train 190 

Dourine,  carriers  of 113 

Drainage,  mosquito  destruction  by 390 

Dresses,  bacillus,  tuberculosis  on 194 

Drinking  cups,  contact  infection  by 189-190 

glass,  bacillus  diphtheriae  on 192 

common,  abolished 210 

Droplet  infection 295-298 

Droplets,  bacillus  influenza;  in 298 

lepra;  in 297 

prodigiosus  in 295-297 

tuberculosis  in 295-296 

pneumococcus  in 298 

streptococcus  salivarius  in 297 

versus  dust 303-305 

Drying,  effect  upon  bacteria. 231-232,  288-289 

resistance  of  bacillus  diphtheria;  to 233,  290 

dysenteria;  to 234 

influenza}  to 238 

pestis  to 235-236,  290-291 

tuberculosis  to ...  .  234-235,  241-242,  291 

typhi  to 232-233,  290 

gonococcus  to 239 

meningococcus  to 238-239 

micrococcus  of  Mediterranean  fever  to 233 

pneumococcus  to 238 

protozoa  to 242 

pus-forming  bacteria  to 236-237 

smallpox  virus  to 244 

spirillum  cholera;  to 237-238,  242,  291-292 

spirochete  of  syphilis  to 239 

spores  to 232 

vaccine  virus  to 242-244 

Dust,  anthrax  spores  in 227 

bacillus  coli  communis  in 294 

diphtheria;  in 290,  294 

pestis  in 290-293 

tuberculosis  in 292-293 

typhi  in 290 

danger  from  sUght 294-295 

infection 288 

meningococcus  in.  •  ■  •  •  •. 289-290,  293 

micrococcus  melitensis  in 21,  300 

pneumococcus  in 293-294 

pus  organisms  in 294 

streptococcus  in 282 

versus  droplets 303-305 

Dust-borne  tliseasc 288-290 

anthrax 285-286 

diarrhea 276-277 

influenza 277 

Mediterranean  fever 312 

pohomyelitis 278 

tuberculosis 288,  291-293,  301-311 


INDEX  461 

PAGE 

Dust-borne  disease,  typhoid  fever 275-27G 

Dwellings,  extension  of  diphtheria  in 197-198 

scarlet  fever  extension  in 196-197 

Dysentery,  see  Bacillary  dysentery. 

amebic 118, 183 

due  to  chronic  carriers 183 

infection  from  bedpan 183 

produced  in  men  by  amebse  grown  in  culture  .       24 

monkeys  by  amebae 24 

transmitted  by  contact 183 

bacilhis,  see  Bacillus  dysenterise. 

due  to  flies 430-431 

infection  by  water 326-329,  331 

Ear  discharge  causes  diphtheria 98 

Elephantiasis 399 

Endemic  diseases 29-30 

EngUsh  hospitals 139-142 

isolation  in . 200-202 

Entameba  coli  and  entameba  histolytica,  distinction  between.  ..24, 118 
Ei-ysipelas  from  rags 222 

Family,  carriers  in,  cerebro-spinal  meningitis 75 

diphtheria 89 

infection  of,  in  house 28,  196-198 

isolation  in 160-161 

typhoid  fever  by  contact  in 176 

Feces,  bacillus  dysenterise  in 24 

paratyphi  in ; 16 

typhi  in 9,  35-36 

persistence  of 10 

intei-mittency  of 46—47 

hookworms  in 187 

spirillum  cholerse  in 19 

Filaria  bancrofti 398 

Filariasis  and  mosquitoes 398-399 

Filth  theory  of  disease 2V 

Filtration  of  water 338 

reduces  typhoid  fever 321 

Fingers  and  contact  infection 188-189 

Fish,  infection  by  fried 278 

Fishermen,  influenza  among 277 

Fleas  and  anthrax 417 

plague 23,  312-313,  413-416 

bacillus  pestis  in 236,  414^15 

Flies  a  nuisance 445-446 

and  anthrax 419 

cholera 430 

diarrhea 431^35 

dysentery 430 

Egyptian  ophthalmia . .     419 

mm-rina 429 

plague 419,  424 

tuberculosis 429 


462  INDEX 

PAGE 

Flies  and  typhoid  fever 169-171,  182-183,  4.35-445 

epidemiological  evidence 442-445 

evidence  against  theory 440-441 

reports  of  outbreaks 435-439 

statistical  evidence 439-445 

bacillus  tuberculosis  in 422-423 

carry  bacillus  anthracis 419,  423 

diphtheria; 423 

dysenteria; 423 

prodigiosu.? 425 

typhi 420-422 

Danysz  rat  virus 424 

fecal  bacteria 425-427 

germs 419-437 

gonococci 424 

lime  from  privies 425 

poliomyelitis 427 

spirillum  choleraj 420 

control  of 445-447 

difficult  to  infect  by 425 

habits  bring  them  in  contact  with  excrement 438 

infected,  in  typhoid  houses 421-422 

local  variation  in  distribution 435,  445 

mechanism  of  infection 424 

range  of  flight 427 

refluction  of  and  decrease  of  typhoid  fever 442-444 

seasonal  and  local  distribution 427 

species  in  houses 428 

tuberculosis  due  to 429 

Flock  cough  from  rags 222 

Floors,  bacillus  pestis  not  on 235 

tetani  in  dirt  of 239 

Fly  specks,  bacillus  tuberculosis  in 422^23 

Fomites:  Bagging 213 

Ballast 213 

Barbers'  utensils 168 

Barracks 76,  216 

Bedding 168, 214 

Blankets 227 

Books 215,  241 

Brush 240 

Cartridges 6,  226 

Charts -.241,  242 

Christmas  presents 215 

Clay 233 

Cloth 213 

Clothing 169,  215-216,  219,  242 

Coat. .  .^ 215,  227 

Communion  cui)s 195 

Cornet 215 

Cotton 214 

Cotl on  goods 228 

Cups 192-193 

Dentists'  tools 168 


INDEX  463 

PAGE 

Fomites:  Drinking  glass 168,  189-190,  192-193,  195,  240 

Floors 235,  239 

Furniture 241 

Gelatine 6,  226 

Glass  blowers'  tubes 168 

Grain 213 

Hair 215,  226,  227 

Handkerchief 168,  234,  240]  293 

Hides 226,  227 

House,  see  Room. 

Lamp  wick 6,  226 

Letters 215 

Linen,  soiled 175,  214,  240 

Lumber 214 

Mattress 213 

Merchandise 213 

Mirror 240 

Money 168,  223,  224 

Napkin  rings 195 

Nursing  bottles 168 

Oyster  buckets 213 

Pencils 168,  193,  233 

Pins 168 

Pitcher 97 

Rags 169,  222 

Railway  carriages 292 

Roller  towel 210 

Room 214,  216,  219-222,  233,  235,  241,  292,  294 

Rugs ■ '  223 

Shawl 409 

Shoes 218,  240 

Spirometer 241 

Spoons,  etc 168 

Struig 168 

Surgeons'  instruments 168 

Telephones 195,  241 

Thermometer 174 

Tools 215 

Toys ■ 240 

Tramcars 292 

Wind  instruments 168 

Wool 226,  227 

Fomites  and  anthrax 226-227 

cholera 215 

diphtheria 215,  227 

plague,  experiments  in  India 246-247 

observations  in  Sydney 245-246 

scarlet  fever 214-215 

smallpox 214 

tetanus 225-226 

tuberculosis,  lack  of  experiments 247 

typhoid  fever 227 

typhus  fever 216-217,  409 

yellow  fever 213-214,  394 


464  INDEX 


Fomites  and  yellow  fever  experiments  in  Havana 245 

bacillus  diphtheria;  on 240-241 

tuberculosis  on 241-242 

bacteria  of  suppuration  on 25 

on 239-240 

clothing  as 216 

conclusions  concerning 258 

definition  of  term 212-213 

evidence  of  infection  by,  unsatisfactory 224-225 

infection,  bacteriological  evidence 230-231 

evidence  against 229-230 

few  instances  of 228 

reasons  for  belief  in 228-229 

thought  important 137 

Food,  carriers  infect 47-51,  60,  65 

handling  by  contacts 162-163 

infection  and  cholera 185 

tuberculosis 364,  372-373 

typhoid  fever 169-170,  364,  374-379 

poisonings 38,  60,  371-372 

spirillum  cholerse  in 20 

Foot-and-mouth  disease  and  milk 366 

French  hospitals 198-200 

"  Antisepsie  mcdicale"  in 198 

cubicles  for  isolation  in 198-200 

screens  for  isolation  in 198-200 

Furniture,  bacillus  diphtheria;  on 241 

Gall  stones  and  typhoid  fever 36,  42 

Gelatine,  bacillus  tetani  in 6,  226 

Glanders,  carriers  of 99 

Glands,  bacteria  of  suppuration  in 25 

cervical  and  mesenteric,  bacillus  t  uborculosis  in 203 

Glass,  bacillus  diphtherite  on 192,  240 

tuberculosis  on 195 

contact  infection  by  drinking  from 189-190 

Glossina  morsitans 113 

palpahs 115,  399-401 

Goats  and  Mediterranean  fever ' 21,  72,  365 

Gonococci  carried  by  Hies 424 

Gonococcus,  not  sapr()i)hy(  i(! 26 

resistan(!(!  to  drying 239 

Gonorrhea,  air-borne  infection  not  jjossible 166-167 

believed  to  be  s|)read  by  cont  act 164-167 

carried  by  nurses 166-167 

in  Babies'  Hospital 165-166 

infection  by  fomites  itnijossible 166-167 

latency  of 102-103 

not  dust-borne 289 

persistence  of 102-103 

Gown  and  cap  for  physicians  and  nurses  in  contagious  cases.  .  .  .      21S 

Grain,  yellow  fever  from 213 

(Jround  s(|uirrels  and  j)lague 413 

Guinea  pigs,  bacillus  pcstis  in 69-70 


INDEX  465 

PAGB 

Hair,  anthrax  spores  in 226-227 

scarlet  fever  from 215 

Handkerchief,  bacillus  diphtherise  on 240 

tuberculosis  on 234,  293 

Hands,  bacillus  coli  communis  on 179,  192 

tuberculosis  on 193-194 

pus  bacteria  on 192-194 

should  be  washed 179-180 

Hazens  theorem 329 

Hides,  anthrax  spores  in 226-227 

Holy  water,  bacillus  diphtherise  in 192 

Homalomyia  canicularis 428 

Home  isolation  effective 160 

Hookworms,  see  Uncinaria,  Anchylostoma 186-187 

enter  through  skin 187 

grow  in  soil 186 

in  feces 187 

Hospital  isolation,  failure  of 139-142 

in. 161 

Hospitals,  air-borne  disease  in 270-271,  279-280 

bacillary  dysentery  in 183-184 

contact  infection  in 198-202 

diphtheria  not  air-borne  in 273-274 

in  America 142-145 

England 139-142 

France 198-200 

scarlet  fever,  not  air-borne  from 272-273 

smallpox,  air-borne  infection  from 260-270 

typhoid  fever  by  contact  in 173-174 

value  of 160 

House,  infection  from  family  to  family 28 

of,  cause  of  scarlet  fever 214-215 

tuberculosis  infection  in 205,  220-222 

Houses,  species  of  flies  in 428 

Ice,  bacillus  typhi  in 13,  319,  341-342 

infection  by 339-342 

Ice  cream,  a  source  of  disease 349-350 

control  of 350 

Incubation  stage  infective 39-40 

Infection,  former  theories  of 1 

not  so  easy  as  believed 84,  153,  191-192 

Influenza  among  fishermen 277 

lighthouse  keepers 277 

atypical  cases 99 

bacillus,  see  Bacillus  influenzae. 

f I'om  rags 222 

not  au'-borne 277 

carried  across  Atlantic 277 

dust-borne 277, 289 

spread  only  by  contact 277 

Inhalation  of  bacteria 304-305 

Insect-borne  disease  usually  due  to  protozoa 380-381 

Insects  as  biological  and  mechanical  cai-riers 380-382 


466  INDEX 

PAQB 

Insects  carry  germs  on  bodies 418 

first  proof  of  transmission  of  disease  by 381-382 

infection  by,  importance  of  subject 380 

Texas  cattle  fever  first  disease  proved  to  be  carried  by.  .  3S 1-382 

Institutions,  carriers  in 50-o2,  65,  67 

Intermittent  excretion  in  carriers 46,  62,  76,  98 

Isolation  a  failm-e  in  cerebro-spinal  meningitis 146 

measles 145-146 

smallpox 147 

causes  of  failure 147-149 

duration  of 160-162 

effective  if  prompt 146,  157-158 

in  Michigan 156-158 

rare  diseases 158-159 

hospitals,  failure  of 139-142 

in  American  cities 142-145 

English  hospitals 200-202 

family 160-161 

effective 160 

hospital 161 

Monsall  Hospital 200-202 

Providence 136,  160 

villages 155-158 

not  effective  in  extensive  outbreaks 158 

to  be  too  strict 151-152 

of  cerebro-spinal  meningitis 146 

diphtheria 136, 137-139,  143,  149,  156 

durat  ion  in  Providence 143 

malaria 388 

measles 145,  156 

plague 415 

rare  diseases 158 

scarlet  fever 136,  139,  156 

school  children 162 

sleeping  sickness 401 

smallpox 139, 147,  156 

typhoid  fever 152,  156 

wage  earners 152,  162-163 

yellow  fever 393 

should  vary 155 

too  rigorous 152-153 

useless  if  many  carriers 159 

value  of 151-152 

Jews  do  not  eat  sliellfish 376 

Kala-azar  and  insects 402 

Kissing  means  of  sjjrcad  of  tuberculosi-i 202-203 

spreading  syphilis 168 

Laboratory  infect  ion,  bacillary  dysentery 183-184 

tyi>lH)id  fever 175 

tuberculosis  infection  in 308-309 

Lamblia ' 1 12 


INDEX  467 

PAGE 

Lampwick,  bacillus  tetani  on 6,  226 

Latency  of  infection  common 106,  122 

Laundress  contracts  smallpox 214 

typhoid  fever 175 

Laundries  and  disease 218-219 

tuberculosis 219 

Leishmania  donovani 402 

tropica 404 

Leprosy,  bacilli  remain  latent 105 

in  clothing 216 

isolation  of 156 

Letters,  scarlet  fever  from 215 

Lettuce,  bacillus  typhi  on 8 

Lice  and  relapsing  fever 412 

typhus  fever  and 405-409 

Light,  bacillus  tuberculosis  perishes  in 234-235 

Lighthouse  keepers,  influenza  among 277 

Linen,  soiled,  smallpox  from 214 

typhoid  fever  from 175,  219 

Lockjaw,  see  Tetanus. 

Luciha  cssar  or  "blue-bottles" 428,  437 

Lumber,  smallpox  from 214 

" Lung  Blocks"  in  New  York 220-222 

Lupus  due  to  inoculation  with  saliva 203 

Malaria,  an  endemic  disease 29-30 

and  insects 382-392 

water 384 

anointing  the  skin  in 389 

clearing  of  space  about  dwellings 389 

discovery  of  insect  transmission 382-383 

^experiments  on  infection  of  human  beings '.  .     383 

isolation  sometimes  necessary 388 

killing  of  mosquitoes  in  houses 388 

latency  of 113-115 

explanation 114-115 

in  children 114-115 

percentage  of 114-115 

mosquito  sole  carrier  of 383-385 

not  air-borne 384 

due  to  soil  infection 30 

from  water 335-336 

on  ship  Argo 335 

screening  of  patients 388 

success  of  mosquito  destruction 390-391 

ways  of  prevention 386-390 

Malta,  Mediterranean  fever  exterminated  at 72 

Malta  fever,  see  Mediterranean  fever. 

Mattress,  yellow  fever  from 213 

Measles  an  air-borne  disease 278-280 

carriers  of Ill 

disinfection  after 253 

isolation  in,  a  failure 145-146 

not  from  soil 28 


468  INDEX 

FAQE 

Measles,  number  attacked Ill 

per  cent  of  children  attacked 145 

Meat  and  tuberculosis 372-373 

infection  by 371-374 

inspection,  federal  control  of 373-374 

Mechanical  carriers  distinguished  from  biological  carriers 413 

Mediterranean  fever  an  endemic  disease 21 

and  contact  infection 312 

dust 312 

goats 21,72,365 

caused  by  milk  from  infected  goats 21,  365 

experiments  in  infection  by  air 311-312 

exterminated  at  Malta 72 

goats  carriers  of 72 

human  carriers  of 72 

in  United  States 365 

micrococcus  of,  resistance  to  drying 233 

on  a  steamship 72 

spread  by  urine 22 

Membrane,  bacillus  diphtherias  in .•••.•. ^^^ 

Meningitis,  cerebro-spinal,  see  Cerebro-spinal  meningitis. 

Meningococcus  causes  rhinitis 73 

found  intermittently 76 

only  near  sick 77 

in  air 77 

contacts 73-74,  76-77,  80 

dust 289-290,  293 

families 75-80 

normal  nose 73 

nose  in  sickness 72 

infection  in  barracks 76 

not  saprophytic 26 

persistence  of  infection 74-75 

resistance  to  drying 238-239 

Merchandise,  yellow  fever  from 213 

Michigan,  isolation  effective  in 156-158 

Micrococcus  albus 24 

aureus 24 

citreus 24 

melitensis,  discovery  and  study  of 21 

in  (hist 21,300 

resistance  to  drying 233 

saprophytic  existence  of 21 

meningitidis,  see  Memingococcus. 
})n('umonia»,  see  Pneumococcus. 

Mild  cases  of  inf(;ctious  disease  not  recognized 134-135 

Milk  and  disease 342-370 

bacillus  (hphtheriai  in 25-26 

dyscnicria!  in 15 

tuberculosis  in 355-356 

typhi  in 15-17 

carriers  infect 52-54 

classification  of 363 

condenscid  and  diarrliea 368-369 


INDEX  469 

PAGE 

Milk,  diarrhea  from 36&-369 

diphtheria  from 96-97,  345-346 

foot-and-moutli  disease  from 366 

handhng  by  contacts 162-163 

increase  of  bacillus  typhi  in 17 

infection  by  water 323 

from  human  sources 347-348 

Mediterranean  fever  from 365 

mode  of  infection  of 347-348 

outbreaks,  characteristics 342-343 

few  in  large  cities 344-345 

frequency  of 343-344 

source  of  infection 346-347 

pasteurization  of 348-349 

protection  against  tuberculosis  from 362-363 

of 348-349 

rabies  from 366 

scarlet  fever  from 346-349 

spirillum  cholera;  in 19 

sterihzation  of  vessels 348 

streptococcus  in 352 

tonsillitis  from 351-352 

tuberculosis  from 354-362 

amount  of 356-362 

epidemiological  evidence 361-362 

instances  of 360 

tuberculous,  consumed  by  children 357-360 

typhoid  fever  from 51-54,  343-345 

Mills-Reincke  phenomenon 329-335 

Miners,  typhoid  fever  among 182 

Minnesota,  smallpox  isolation  abandoned  in 147 

Mirror,  bacillus  diphtherice  on 240 

Missed  cases  a  recent  discovery 33 

Moist  surfaces,  bacteria  not  given  off  from 287-288 

Money  and  disease 223-224 

bacteria  on 223-224 

Monkeys,  dysentery  in 24 

Monsall  Hospital,  isolation  in 200-202 

Montana,  smallpox  isolation  abandoned  in 147 

Mosquito  destruction  by  culicides 390,  397 

drainage 390 

oihng 390 

prevention 389-391 

Mosquitoes  and  dengue 409-410 

filariasis 398-399 

malaria 382-383 

conditions  for  carrying 385-386 

yellow  fever 392-398 

destruction  of 397 

habits 395 

destruction  of,  in  malarious  houses 388 

habits  of .  ."". 385 

species  which  carry  malaria 382-383,  385 

success  of  measiu-es  for  extermination 390-391 


i70  INDEX 

PAGE! 

Mosquitoes,  transportation  of 395 

Mouth,  bacillus  tuberculosis  in 103-104,  193 

pneumococcus  in 101-102 

Mucous  surfaces,  bacteria  of  suppuration  on 24 

Mud  dumped  near  intake  cause  of  typhoid  fever 320 

Municipal  versus  personal  prevention 208 

Murium  typhi,  bacilli  of,  carried  by  ants 419 

Murrina,  flies  and 429 

Musca  domestica  (see  FUes) 418,  428,  437 

Muscina  stabulans 428 

Mussels,  infection  by 375-377 

Myzomyia  ludlowii 385 

Nagana 113 

Night  soil  as  a  fertilizer 9 

North  Boston  well 317 

Nose,  bacillus  tuberculosis  in 103-104,  193,  299 

meningococcus  in,  in  sickness 72-73 

in  normal 73 

tuberculosis  of 204 

Nurses,  gown  and  cap  for,  in  contagious  cases 218 

infect  patients  with  typhoid  fever 174 

typhoid  fever  among 173-174 

Oiling,  mosquito  destruction  by 390 

OphtTiahnia,  Egyptian,  carried  by  flies 419 

Opilacao  due  to  connorrhinus 403 

Opsonic  index  in  typhoid  carriers 42 

Oriental  sore  and  insects 404 

Ornithodorus  moubata 411 

Otitis,  bacillus  diphtheriae  in 94-95 

Owatonna,  Minn.,  diphtheria  in 144 

Oyster  buckets,  yellow  fever  from 213 

Oysters,  bacillus  typhi  in 14 

"fattening"  of 377 

infection  by 374-378 

Pail-closets  cause  typhoid  fever 181-182 

Pappataci  fever  and  insects 404 

Paratyphoid  bacilli,  see  Bacillus  paratyphi. 

fever 58-61 

Pediculis  vestamenti  and  typhus  fever 405-409 

Pellagra  and  insects 403 

Pencils,  bacillus  ilii)htheria}  on 193,  233 

bacteria  on 192-193 

Personal  versus  municipal  prevention 208 

Persons,  not  things,  are  dangerous 225 

Phlehotamus 404i)  405 

Physicians,  gown  and  cap  for,  in  contagious  cases 218 

rarely  carry  disease 217 

Pigment  to  lungs  from  stomach 306 

Piro|)lasma  bigcmimun 112,  381-382 

i'lacards  for  contagious  diseases 151 


INDEX  471 

PAGE 

Plague,  air-borne 281 

and  bedbugs 414 

fleas 23,  312-313,  413-416 

epidemiological  evidence 414-415 

experimental  work > 414-415 

flies 419,425 

fomites,  experiments  in  India 246-247 

observations  in  Sydney 245-246 

ground  squirrels 413 

other  rodents 413-416 

rats 23,  6&-70,  413-416 

rugs 223 

atypical  and  chronic  in  animals 69-70 

human 70 

bacillus,  see  Bacillus  pestis. 

experiments  in  infection  by  air 312-313 

isolation  of 415-416 

not  dust-borne 289-290 

Plasmodium 113,  384-385 

Pneumococcus  cause  of  meningitis 81 

in  air 300 

convalescents 101 

droplets 298 

dust 293-294 

normal  mouths 101-102 

may  be  air-borne 289 

not  dust-borne 290 

saprophytic 26 

persistence  of 101 

resistance  to  drj-ing 238 

virulence  of,  in  carriers 101-102 

Pneumonia  and  water 333 

Poisoning  by  food 371-372 

PoliomyeUtis  a  dust-borne  disease 278 

atypical  cases 121-122 

carried  by  flies 427 

carriers  of 118-121 

Privies  and  water-closets  usually  filthy 179-180 

encourage  uncleanhness 182,  211 

infect  water  suppUes 320 

removal  of,  causes  decrease  of  typhoid  fever 181-183 

typhoid  fever  from 169-170,  179-183 

Privy  vaults,  bacillus  typhi  in 9-10 

Prosedemic  infection,  typhoid  fever  by 172 

Prostatic  fluid,  bacillus  typhi  in 37 

Proteosoma  in  birds 383 

Protozoa,  difficult  to  cultivate 27 

not  saprophytic 26 

resistance  to  drying 242 

Protozoan  disease,  carriers  a  source  of 126 

latency  in 111-112 

Psocidae  and  disease 418 

Pulex  irritans 414 

Purification  of  water 338^339 


472  INDEX 

I  AGE 

Pus  bacteria 24 

distribution  of 240 

in  air 299-300 

dust 294 

glands 25 

schoolrooms 294 

skin  and  mucous  surfaces 24 

tonsils 24 

water 25 

may  be  dust-borne 2S9-290 

on  f omifes 25 

resistance  to  drying 236-237 

saprophytic  existence  of 24-25 

Quarantine  and  sleeping  sickness 401 

yellow  fever 396 

Quinia  prevents  malaria 386-388 

Rabies  from  milk 366 

Radishes,  bacillus  typhi  on 8 

Rags  and  disease 222-223 

cholera  from 222 

erysipelas  from 222 

flock  cough  from 222 

influenza  from 222 

scarlet  fever  from 222 

septicemia  from 222 

smallpox  from 222-223 

typhoid  fever  from 222 

Railway  carriages,  bacillus  tuberculosis  in 292 

Rat-proofing  of  buildings 416 

Rats  and  plague 23,  69-70,  413-416 

carriers  of  plague 70 

chronic  plague  in 69 

destruction  of 416 

Relapsing  fever  and  bedbugs 411-412 

hce 412 

ticks. 410-411 

infectious  during  afebrile  period 116 

types  and  parasites 116 

Resistance  of  bacteria  less  in  cultures 11 

Rhinitis,  bacillus  dii)htheria;  in 94-95 

caused  by  meningococcus 73 

Rhode  Island,  death  rate  from  tyi)lu)id  fever 18 

Rice,  spirilhim  choleric  in 20 

Ro(!ky  Mountain  fever  and  tic^ks 412 

Rodents,  plague  derived  from 413-416 

Roller  towel,  bacillus  coli  connnunis  on 192 

should  be  al)olished 210 

use  of,  forl)i(lden 211 

Room,  baciillus  diphtherias  in 233,  241 

tuberculosis  in 235 

inf(!ction  (rause  of  typhoid  fever  in  barracks 210 

Rooms,  infection  of 205,  214-215, 219-222 


INDEX  473 

PAGE 

Rubella,  air-borne 280 

Rugs  and  plague 223 

Saliva,  inoculation  with,  cause  of  lupus 203 

transfer  of 189 

vehicle  of  infection 188-190 

Sarcophaga 428 

Scarlet  fever,  air-borne 270-273 

out  of  doors 272-273 

and  books 215 

clothing "217 

coat 215 

fomites 214-215 

house  infection 214-215 

letters 215 

milk 346-347 

rags 222 

atypical. 107-109 

disinfection  unnecessary  after 250-252 

due  to  ice  cream 350 

extension  in  dwellings 196-197 

hospital  temporarily  closed  in  Leicester 141 

hospitals  in  England 139-142 

in  cows. 346-347 

in  Providence 136 

Uke  diphtheria 106-107 

not  air-borne  from  hospitals 272-273 

from  soil 28 

virulence  varies  in 140 

Scenopinus  fenestrahs 428 

,Schizotrypanum  cruzi 404 

School  children,  isolation  of -  162 

disinfection 2M 

teaching  cleanliness  in 209-210 

Schoolrooms,  bacillus  coli  communis  in 294 

pus  organisms  in 294 

Screening  for  protection  against  malaria 388 

of  cases  of  malaria 388 

yellow  fever 396-397 

Screens  for  isolation  in  French  hospitals 198-200 

Sedgwick,  typhoid  fever  outbreak  in  Bondville,  Mass 169 

Seltzer  water,  baciUus  typhi  in 13 

Seminal  vesicles,  baciUus  tyjihi  in 37 

Septic  infection  and  insects 417—418 

tank  effluent,  bacillus  tj^phi  in 10 

Septicemia  from  rags 222 

Sewer  air  and  bacteria 284-285 

diphtheria 273 

typhoid  fever 274-275 

bacillus  prodigiosus  in 284 

typhi  in 284 

infection  by 297,  299 

Sex  of  smallpox  cases 267 

Sheet  hmig  before  door  to  prevent  infection 282 


474  INDEX 

PAGE 

Shellfish,  infection  by 374-378 

Shipboard,  influenza  on 277 

malaria  on 335 

typhoid  fever  bj^  contact  on 176 

Ships  for  smallpox  hospitals 262-263 

Shoes  as  carriers  of  infection 218 

bacillus  diphtherise  on 240 

Shuttle,  infection  from 192 

Sidewalks,  virulent  baciUi  tuberculosis  on 194 

SimuUum 403 

Skin,  bacteria  of  suppuration  in 24 

hookworms  enter  through 187 

Sleeping  sickness,  an  endemic  disease 30 

and  tsetse  flies 399-401 

atoxyl  to  prevent 402 

discovery  of  trypanosome 399-400 

in  lower  animals 400 

is  it  carried  mechanically? 400-401 

modes  of  transmission 399-401 

not  due  to  soil  infection 30 

per  cent  of  carriers 115-116 

persistence  of  infection 115-116 

prevention  of 401-402 

quarantine 401 

Smallpox,  air-borne,  conclusions 269-270 

evidence  against 266-269 

"  infection  of,  denied 263-270 

in  United  States 264-265 

objections  to  theory 265-266 

sex  of  cases 267 

and  fomites 214 

rags 222-223 

atypical  cases 109-110, 133 

carriers 109-1 10 

hospital  ships 262-263 

isolation  in,  often  a  failure 147 

mild  cases  of 109-110 

not  from  soil 28 

virus,  resistance  to  drying 244 

Soft  drinks,  bacillus  typhi  in 13 

Soil,  amcba)  dysenteriai  in 24 

bacillus  diphtheriic  in 26,  28 

dysenterite  in 23 

pestis  in 22 

tetani  in 239 

typhi  in 7,  10 

hookworms  grow  in 186 

infect  ion,  cliolcra  from 29 

in  conunon  diseases 28 

typhoid  fever  from 29 

melitensis  micrococcnis  in 21 

not  infected  with  cattle  fever 30 

malaria 30 

measles 28 


INDEX  475 

PAGE 

Soil,  not  infected  with  scarlet  fever 28 

sleeping  sickness 30 

smallpox 28 

Texas  cattle  fever 30 

yellow  fever 30 

spirillum  cholerse  in 19-20 

Sore  throat  and  milk 351-352 

Spanish-American  War,  typhoid  fever  in 17,  56,  435 

from  dust  in 275-276 

flies ; 435-436 

Spirillum  cholerse  carried  by  flies 420 

found  in  water 326 

grow  only  in  human  body 20 

in  convalescents 61-62 

cooked  food 20 

dead  bodies 19 

feces 19 

gall  bladder 62 

healthy  persons 62-65 

milk 19 

soil 19,20 

water 19 

intermittent  excretion 62 

resistance  to  drying 237-238,  242,  291-292 

saprophytic  existence  of 19 

Spirocheta  carteri 116,  412 

duttoni. 116,  411 

Spirochete  of  syphilis,  latency  of 116 

not  saprophytic 26 

resistance  to  drying 239 

Spirometer,  bacillus  diphtheriae  not  on 241 

tuberculosis  not  on 195 

Spitting  should  be  forbidden 211 

Spores  may  be  dust-borne 290 

resistance  to  drying 232 

Springs  as  sources  of  infection 324 

Sputum,  bacillus  pestis  in 71 

tj-phi  in 37-38 

Squirrels,  see  Ground  squirrels  (Citellus  beecheyi). 

Stamp  out  disease,  failure  to 135-136 

Stegomyia  calopus 392,  395,  405 

Sterilization  of  municipal  water  supplies 339 

Stomach,  bacillus  tuberculosis  may  pass  to  lungs  from 305-308 

Stomoxys  calcitrans 428 

Storage  of  water 338 

Street  dust,  bacilli  tuberculosis  not  found  in 292 

Streptococcus  enteritidis,  cause  of  diarrhea 367 

in  dust 282 

milk 352 

may  be  air-borne 289 

pyogenes 24 

saUvarius  in  droplets 297 

Suppuration,  bacteria  of,  in  healthy  organs 105-106 

latency  of  bacteria  of 105-106 


476  INDEX 

PAGE 

Suppuration,  result  of  infection  by  bacteria 24 

Surgery,  air-borne  infection  in 283-284 

Swine  infected  by  bacillus  tuberculosis  through  the  tonsils ....  203-204 

plague  bacilli  in  air 300 

Syphilis,  au'-borne  infection  not  possible 167 

articles  infected  with 168-169 

beheved  to  be  spread  by  contact 164-169 

droplet  infection  in 167 

fomites  infection  in,  not  important 169 

infection  by  kissing .  168 

non-sexual  contact 168-169 

latency  of 116 

not  persistent 168-169 

sexual  act  chief  mode  of  infection 168 

spirochete  of,  see  Spirochete  of  syphihs. 

spread  solely  by  contact 167-168 

Tabanus  lineola 3 

Teacher  caused  diphtheria 97 

contracts  diphtheria  from  pupil 98 

Telephones,  bacillus  diphtheria;  not  on 241 

tuberculosis  on 195 

Tetanus  and  fomites 225-226 

bacillus,  see  Bacillus  tetani. 

decrease  of,  in  Havana 226 

from  lamp  wick  used  for  tying  umbiUcal  cord 5,  226 

in  Red  Bank,  N.J 5 

on  Long  Island 5 

Texas  cattle  fever,  an  endemic  disease 30 

carried  by  tick 112 

fh'st  disease  proved  to  be  carried  by  insects. 38 1-382 

not  due  to  soil  infection 30 

persistence  in  blood 112 

Thermometer  transfers  bacillus  typhi 174 

Things  not  so  dangerous  as  persons 225 

Ticks  and  relapsing  fever 410-411 

Rocky  Mountain  fever 412 

Texas  miile  fever 112,  122,  381-382 

Tidal  mud,  bacillus  typhi  in 8 

Tongue,  bacillus  tuberculosis  on 203 

Tonsilhtis  and  milk 351-352 

Tonsils,  bacillus  tuberculosis  in 203-204 

typhi  in 34 

bacteria  of  sui)j)urat  ion  in 24 

tuberculosis  infection  through 306 

of 204 

Tools,  diphtheria  from 215 

Towel,  see  lioller  towel. 

Toys,  l)acilhis  diplitlicria  on 240 

Tramcars,  bacillus  tuberculosis  in 292 

Treasurer  of  United  States,  investigation  of  money  as  carrier  of 

disease  by ... 224 

Treponema  pallida  in  gummata 116 

life  of,  short 167, 169 


INDEX  477 

PAGE 

Trier,  typhoid  fever  in 17,  57 

Trypanosoma  bruccei 113 

cquiperdum 113 

gambiense tl5,  399-401 

Tsetse  flies  and  sleeping  sickness 115,  399-401 

nagana 113 

Tuberculosis  and  flies 429 

fomites,  lack  of  experiments 247 

laundries 219 

meat 272-273 

bacillus,  see  Bacillus  tuberculosis. 

bovine,  eradication  of 304 

contact  infection  in 204-205 

experiments  concerning  air-borne  infection 301-311 

feeding  experiments 354-355 

from  flies 429 

house  infection 220-222 

milk 354-368 

amount  of 356-362 

epidemiological  evidence 361-362 

instances  of 360 

protection  against 362-363 

■  shuttle 192 

water 332-333 

human  and  bovine  reciprocally  infective 353 

infection  by  air 194,  202-203 

dust  questioned 302-303 

in  the  home 205 

stomach 305-308 

experiments  under  natural  conditions. .  .309-311 

in  alimentary  tract 203-204 

animals  through  mouth  and  pharynx  204,  306 

laboratory 308-309 

unnatural  conditions  of  experiment 308 

mode  of  infection,  evidence  from  pathology 205 

of  the  nose 204 

tonsils 204 

proportion  of  human  and  bovine  types  of  baciUus  360-361 

spread  by  animals  Ucking  one  another 204 

kissing 202-203 

through  tonsils 204,  306 

Tuberculous  milk  consumed  by  children 357-360 

Typhoid  bacillus,  see  Bacillus  typhi. 

carriers 18,  38-55, 180 

cannot  be  isolated 152 

cause  disease 47-54 

infective  during  incubation  stage 39-40 

number  of 180 

opsonic  index  in 42 

percentage  of 40-44 

feces  in  yard 170, 173, 182 

fever  among  nurses 173-174 

an  infection  of  the  blood 34-35 

and  gall  stones 36,  42 


478  INDEX 


Typhoid  fever  and  high  temperature 374-375 

tonsiUitis 34 

atypical 56-59 

*     behaved  to  be  an  intestinal  disease 178 

by  bathing 324-325 

contact 17,  47-51,  169-183 

in  an  almshouse 175 

civdlife 171-173 

hospitals 173-174,  436 

South  Africa 171,  436 

Spanish  War 170-171,  435-436 

the  family 176 

on  shipboard 176 

food  infection 169-170 

prosedemic  infection 172 

carriers  of,  among  different  classes 39-44 

duration  of  infection 45 

causes  of  excess  in  cities 321 

contact  outbreaks  in  cities 172-173 

contracted  by  laundress  from  soiled  linen 175 

death  rate  in  Rhode  Island 18 

decreases  with  removal  of  privies 181-183 

filthy  habits  cause  of 170,  173, 182 

from  bedbugs 418 

celery 379 

clothing 219 

crawfish 378 

cream 349 

dust 275-276 

flies 169-171, 182-183,  435-447 

correlated  decrease 442-444 

seasonal  distribution 439-442 

statistical  evidence 439-445 

fomites 227 

handling  typhoid  cultures 175 

ice  cream 349-350 

infected  bedding 175 

milk 51-54,  345-346 

mud  dumped  near  intake 320 

pail  closets 181-182 

privies 169-170,  179-183 

rags 222 

sewer  air 274-275 

shellfish 374-378 

soil  infection 29 

soiled  linen 219 

springs 324 

tlicrmomoter 174 

unrecognized  cases 133 

water 317-325 

wat  crcross 378-379 

wind  blowing  sewage  to  water  works 320 

houses,  infected  flies  in 421-422 

in  barracks  due  to  room  infection 216 


INDEX  479 

PAGE 

Typhoid  fever  in  mines 182 

soldiers'   home  due  to  contact  infection  from 

physician 175 

Spanish  War 17,  56, 435 

Trier :••••; 17 

waitress  due  to  contact  infection 175 

infection  stopped  by  strict  cleanUness 174 

less  with  water  closets 181-182, 144 

mild  cases  in  Panama 57 

Spanish  War 56 

Trier 57 

not  an  intestinal  disease 34 

dust-borne. 289-290 

outbreaks  continued  by  contact  infection 172-173 

in  Providence,  R.  1 18 

prevalent  in  country 173 

spread  among  patients  by  nurses 174 

by  kitchen  help 175 

waitress 175 

"Typhoid  Mary " 47 

Tjrphus  fever  and  flies 408 

hce 405-409 

carried  in  shawl 409 

considered  air-borne 408 

from  clothing 216-217 

identity  of  strains 409 

not  air-borne 281 

of  extra-corporal  origin 29 

Uncinaria,  see  Hookworms,  Anchylostoma. 

americana 186 

due  chiefly  to  contact 186-187 

Urine,  bacillus  typhi  in 37 

persistence  of 10 

cause  of  Mediterranean  fever 22 

Vaccine,  resistance  to  drying 243-244 

transport  across  ocean 242-244 

Vaginitis  in  Babies'  Hospital 165-166 

Vegetables,  amebse  dysenterise  on 24 

bacillus  typhi  on 8 

Venereal  diseases,  see  Gonorrhea;  SyphiUs. 

Vincent's  angina 117 

Wage  earners,  isolation  of 152,  162-163 

Waitress,  typhoid  fever  spread  by 175 

Warning  sign  in  diphtheria 151 

Washing  soiled  linen  in  running  streams  cause  of  cholera 325 

Water  and  cholera 325-326 

diarrhea 327-329,  331 

dysentery 326-329,  331 

malaria. 335,  384 

pneumonia 333 


480  INDEX 


Water  and  the  general  death  rate 331 

tuberculosis 332-333 

typhoid  fever 317-325 

worms 336 

yellow  fever 336 

bacillus  tj^phi  in 10-13,  319 

recovered  from 319 

bacteria  of  suppuration  in 25 

closets,  typhoid  fever  less  with 181-182 

filtration  of 338 

infection  by 316-339 

of 18 

milk  by..  . 323 

micrococcus,  meUtensis  in 21 

mode  of  infection  with  tyjihoid  bacilli 320 

municipal  supphes  infected 320,  326 

outbreaks,  characteristics 317-319 

protection  of 337-338 

purification  of 338-339 

spirillum  cholerae  in 19 

sterilization  of  municipal 339 

storage  of 338 

Watercress,  tyi)hoid  fever  caused  by 378-379 

Wells,  amount  of  typhoid  fever  due  to 322-324 

cholera  infection  from 325-326 

conditions  of  safety 324 

infection  from 316-317,  321-325 

protection  of 337 

White  diarrhea  of  chicks 71 

Whooping  cough,  air-borne 280 

not  of  extra-corporal  origin 29 

Willard  State  Hospital,  diphtheria  in.  .  . 144 

Wind  blowing  sewage  to  water  works  cause  of  typhoid  fever 320 

Wool,  anthrax  from 227 

spores  in 226-227 

Worms  derived  from  water 336 

Wounds,  infection  of,  by  air 300-301 

Yellow  fever  an  eiidcmic;  disease 30 

and  bagging 213 

ballast 213 

cloth ..      213 

•      fomites 213-214,  394 

experiments  in  Havana 245 

grain 213 

mattress 213 

merchandise 213 

mosquitoes 293-298 

oyster  buckets 213 

quarani  ino 396 

discovery  of  causation 392-394 

latent,  period  in  outbreaks 393-394 

mild  and  atypical  cases 117 

mosciuitu  destruction 397 


INDEX  481 

Yellow  fever  mosquito,  habits  of 395 

not  due  to  soil  infection 30 

from  water 336 

preventive  measures ". ' '  ' '  .396-397 

screening  of  cases  and  houses '  '  .  396-397 

success  of  mosquito  destruction 391  395  397-398 

virus  filterable '.393-394 

1^  blood 393-394 


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